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697 451 1938 




HEATING VENTILATING 

AIR CONDITIONING 

GUIDE 1938 



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TECTED SY COPYRIGHT .A.ND NOTHING 
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HEATING VENTILATING 
AIR CONDITIONING 

GUIDE 

1938 

AN INSTRUMENT OF SERVICE PREPARED FOR THE PROFESSION CONTAINING A 

Technical Data Section 

OF REFERENCE MATERIAL ON THE DESIGN AND SPECIFICATION OF HEATING, 
VENTILATING AND AIR CONDITIONING SYSTEMS BASED ON THE TRANS- 
ACTIONS THE INVESTIGATIONS OF THE RESEARCH LABORATORY AND CO- 
OPERATING INSTITUTIONS AND THE PRACTICE OF THE MEMBERS AND 
FRIENDS OF THE SOCIETY 

TOGETHER WITH A 

Manufacturers 9 Catalog Data Section 

CONTAINING ESSENTIAL AND RELIABLE INFORMATION CONCERNING 
MODERN EQUIPMENT 

ALSO 

The Roll of Membership of the Society 

WITH 

Complete Indexes 

TO TECHNICAL AND CATALOG DATA SECTIONS 

Vol. 16 

$5.00 PER COPY 
Copyright, 1938 

AND 

PUBLISHED ANNUALLY BY 

AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS 

51 MADISON AVENUE .'. NEW YORK, N. Y. 



"TO THE isth EDITION 

J^HE acceptance of the HEATING, VENTILATING, AIR 

CoxDiTi6>'i> : G t GUIDE as an authoritative source of scientific infor- 
mation on all engineering phases of the industry, has imposed each year 
since 1922 more and greater responsibilities on the Guide Publication 
Committee. Although extensive new material has been added to this 
edition, the ideals of the founders have been carefully preserved by pre- 
senting only authentic and current investigative results which have been 
tried and accepted in practice. 

The sequence and arrangement of the various chapters have been 
changed to provide for a more logical grouping according to related 
subject matter, and a visual chapter index has been added. Probably, 
the greatest changes that have been made in the text are those relating 
to cooling phases of the industry. The chapters on Refrigerants and Air 
Drying Agents, Cooling Load, Central Systems for Cooling and Dehu- 
midifying and Cooling and Dehumidification Methods have been entirely 
revised to bring them up-to-date and to correlate them more closely. 
One entirely new chapter on Air Conditioning in the Treatment of 
Disease was introduced in this edition which outlines many of the appli- 
cation requirements found in the medical field. Some minor changes were 
made in the chapters on Heat Transmission Coefficients, Air Leakage, 
Heat and Fuel Utilization, Heating Boilers and Steam Heating Systems. 

The chapters have been rewritten which deal with Air Pollution, 
Automatic Fuel Burning Equipment, Hot Water Heating Systems and 
Piping, Spray Equipment for Humidification and Dehumidification, Air 
Cleaning Devices, Railway Air Conditioning, Industrial Air Conditioning, 
Piping and Duct Insulation, Electrical Heating and Radiant Heating. 

The Catalog Data Section of the GUIDE is receiving more recognition 
as each issue appears for the valuable product data contained therein. 
As usual, the manufacturers have cooperated in accomplishing the dual 
purpose of this part of the GUIDE; to provide authoritative and condensed 
catalog information for the Guide user, and to develop an effective and 
productive advertising medium for the manufacturer. 

In offering the 16th edition of the HEATING, VENTILATING, AIR CON- 
DITIONING GUIDE, the Committee wishes to acknowledge not only the 
editorial assistance unselfishly given by many whose aid is specifically 
accredited elsewhere, but also the valuable suggestions offered by the many 
readers and users of other editions. It is hoped that improvements 
and additions will be suggested to future Committees by readers of 
this volume, particularly, as perfection is not of human attainment. 

Without the publication of previous editions, the issuance of the 
HEATING, VENTILATING, AIR CONDITIONING GUIDE 1938 in this fairly 
complete state m so short a time would be practically impossible. It is 
the Committee s^hope that the same enthusiastic reception* given to 
earlier volumes will be accorded this edition of 15,500 



: V, Chairman 

# 

GUIDE PUBLICATION COMMITTEE 



CONTENTS 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

PAGE 

TITLE PAGE i 

PREFACE.- ii 

CONTENTS iii-v 

EDITORIAL ACKNOWLEDGMENT iv 

CODE OF ETHICS FOR ENGINEERS vi 

INDEX TO TECHNICAL DATA vii 

TECHNICAL DATA SECTION 1-840 

CATALOG DATA SECTION 841-1162 

INDEX TO ADVERTISERS 843 

INDEX TO MODERN EQUIPMENT 1165 

ROLL OF MEMBERSHIP. 1-80 

SECTION I. PRINCIPLES 

Chapter 1. Air, Water and Steam... 1 

Chapter 2. Refrigerants and Air Drying Agents 35 

Chapter 3. Physical and Physiological Principles of Air Conditioning.... 51 

Chapter 4. Air Pollution... _ 79 

SECTION II. BASIC DATA AND COMPUTATIONS 

Chapter 5. Heat Transmission Coefficients and Tables.. 89 

Chapter 6. Air Leakage. 121 

Chapter 7. Heating Load 133 

Chapter 8. Cooling Load 147 

SECTION III. COMBUSTION AND UTILIZATION OF FUELS 

Chapter 9. Fuels and Combustion 165 

Chapter 10. Chimneys and Draft Calculations 179 

Chapter 11. Automatic Fuel Burning Equipment 201 

Chapter 12. Heat and Fuel Utilization 229 

SECTION IV. STEAM AND HOT WATER HEATING SYSTEMS 

Chapter 13. Heating Boilers 243 

Chapter 14. Radiators and Gravity Converters... 263 

Chapter 15. Steam Heating Systems 276 

Chapter 16. Piping for Steam Heating Systems.- 301 

Chapter 17. Hot Water Heating Systems and Piping 331 

Chapter 18. Pipe, Fittings and Welding 35 

(Continued on Page V) 



EDITORIAL ACKNOWLEDGMENT 

T70R 16 years the HEATING, VENTILATING, AIR CONDITIONING GUIDE 
I/ has been published by the AMERICAN SOCIETY OF HEATING AND 
VENTILATING ENGINEERS and it retains its leadership asjthe authoritative 
reference volume of the profession and its allied industries. Its users are 
legion and they have adopted The Guide as their standard reference 
source because they recognize that the data are unbiased, up-to-date and 
readily usable. This has been made possible because of the willingness of 
hundreds of technical experts to contribute freely from their knowledge 
and practical experience for the advancement of the profession. 

To the following individuals the Guide Publication Committee is 
profoundly grateful for their assistance in the production of the 1938 
edition, and also to those former contributors who have previously 
prepared a firm foundation for the addition of new material. 



H. E. ADAMS 
T. N. ADLAM 

. C. ALBRIGHT 

!. L. ALT 
0. W. ARMSPACH 
C. L. ARNOLD 
C. M. ASHLEY 
PROF. LL. BEAL 

F, R. BICHOWSKY 
J. L. BLACKSHAW 
M. G. BLUTH 

C. A. BOOTH 
C. J. BRAATZ 

C. E. BRONSON 
PROF. A. I. BROWN 
C A. BULKELEY 
W. H. CARLTON 

P. D. CLOSE 
SABIN CROCKER 
R. C. CROSS 

D. N. CROSTHWAIT, JR. 
PHILIP DRINKER 

G. G. EARLY, JR. 

E. V. ERICKSON 
C. E. ERNST 
JOHN EVERETTS, JR. 
PROF. M. K. FAHNESTOCK 
W. L. FLEISHER 

W. G. FRANK 
J. E. GODFREY 



C D. GRAHAM 
W. A. GRANT 

'. R. HERTZLER 

:. G. HILLIER 

F. C. HOUGHTEN 

PROF. C. M. HUMPHREYS 

H. F. HUTZEL 

L. P. HYNES 

A. J. JOHNSON 

E. F. JONES 

C. F. KAYAN 

R. T. KERN 

R. E. KEYES 

PROF. V. O. KNUDSEN 

PROF. S. KONZO 

PROF. A. P. KRATZ 

PROF. G. L. LARSON 

L. L. LEWIS 

S. R. LEWIS 

H. A. LOCKHART 

ARTHUR MCCUTCHAN 

PROF. L. G. MILLER 

PROF. P. E. MOHN 

L. L. MUNIER 

,H. C. MURPHY 

PROF. D. W. NELSON 

P. NICHOLLS 

R. F. NORRIS 

A. J. OFFNER 

0. W. OTT 



k : 



:S. PARKINSON 
. G. RAPPOLT 
PROF. T. F. ROCKWELL 
J. 0. Ross 

S. I. ROTTMAYER 

PROF. F. B. ROWLEY 
. S. SANDFORT 

:OF. W. M. SAWDON 
PROF. L. E. SEELEY 
LESTER SEELIG 
C. G. SEGELER 
A. M. SELVEY 

C. D. SHIELDS 
R. W. SHIELDS 
A. L. SIMISON 

D. C. SIMPSON 
T. H. SMOOT 

A. E. STAGEY, JR. 
D. J. STEWART 
C. A. THINN 
R/ J. THOMPSON 
W. W. TIMMIS 
PROF. G. L. TUVE 

. H. VAN ALSBURG 

'. 0. URBAN 
A. R. WALKER 
J. H. WALKER 
PROF. G. B. WILKES 

M. S. WUNDERLICH 

PROF. C. P. YAGLOU 



The members of the Society are especially indebted to these engineers 
who have aided in the preparation of this volume and the Guide Publi- 
cation Committee hereby expresses its appreciation for the loyal coopera- 
tion of the many contributors to this 16th edition. 

GUIDE PUBLICATION COMMITTEE 
ALBERT BUENGER, Chairman 



S. H. DOWNS 
C. H. B. HOTCHKISS 
E. N. MCDONNELL, Advisory 



S. S. SANFORD 
W. H. SEVERNS 
JOHN JAMES, Technical Assistant 



CONTENTS (Concluded) 



SECTION V. AIR SYSTEMS PAGE 

Chapter 19. Gravity Warm Air Furnace Systems 377 

Chapter 20. Mechanical Warm Air Furnace Systems 393 

Chapter 21. Central Systems for Heating and Humidifying 409 

Chapter 22. Central Systems for Cooling and Dehumidifying 423 

Chapter 23. Unit Heaters, Ventilators, Air Conditioning, Cooling Units 435 

Chapter 24. Cooling and Dehumidification Methods 469 

Chapter 25. Spray Equipment for Humidification and Dehumidification,. 499 

Chapter 26. Air Cleaning Devices 519 

Chapter 27. Fans 531 

Chapter 28. Air Distribution 547 

Chapter 29. Air Duct Design.- 563 

Chapter 30. Sound Control 583 

SECTION VI. GENERAL 

Chapter 31. Air Conditioning in the Treatment of Disease 597 

Chapter 32. Railway Air Conditioning 60S 

Chapter 33. Industrial Air Conditioning 62] 

Chapter 34. Industrial Exhaust Systems 63c 

Chapter 35. Drying Systems 64' 

Chapter 36. Natural Ventilation.- 669 

Chapter 37. Automatic Control 683 

Chapter 38. Motors and Controls 703 

Chapter 39. Piping and Duct Insulation 719 

Chapter 40. Electrical Heating 741 

Chapter 41. Radiant Heating 753 

Chapiei" 42 District Heating 765 

Chapter 43. Water Supply Piping and Water Heating 783 

Chapter 44. Test Methods and Instruments.. 807 

Chapter 45. Terminology 819 



CODE of ETfflCS for ENGINEERS 

ENGINEERING work has become an increasingly important factor 
in the progress of civilization and in the welfare of the community. 
The engineering profession is held responsible for the planning, construc- 
tion and operation of such work and is entitled to the position and 
authority which will enable it to discharge this responsibility and to 
render effective service to humanity. 

That the dignity of their chosen profession may be maintained, it is 
the duty of all engineers to conduct themselves according to the principles 
of the following Code of Ethics: 

1 The engineer will cany on his professional work in a spirit of fairness 
to employees and contractors, fidelity to clients and employers, loyalty 
to his country and devotion to high ideals of courtesy and personal 
honor. 

2- He will refrain from associating himself with or allowing the use of his 
name by an enterprise of questionable character. 

3 He will advertise only in a dignified manner, being careful to avoid 
misleading statements. 

4 He will regard as confidential any information obtained by him as to 
the business affairs and technical methods or processes of a client or 
employer. 

5 He will inform a client or employer of any business connections, in- 
terests or affiliations which might influence his judgment or impair the 
disinterested quality of his services. 

6 He will refrain from using any improper or questionable methods of 
soliciting professional work and will decline to pay or to accept com- 
missions for securing such work. 

7 He will accept compensation, financial or otherwise, for a particular 
service, from one source only, except with the full knowledge and 
consent of all interested parties. 

8 He will not use unfair means to win professional advancement or to 
injure the chances of another engineer to secure and hold employment. 

9 He will cooperate in upbuilding the engineering profession by exchang- 
ing general information and experience with his fellow engineers and 
students of engineering and also by contributing to work of engineering 
societies, schools of applied science and the technical press. 

10 He will interest himself in the public welfare in behalf of which he will 
be ready to apply his special knowledge, skill and training for the use 
and benefit of mankind. 



INDEX 



HEATING VENTILATING Am CONDITIONING 
GUIDE 1938 

Technical Data Section 
Chapters 1-45 and Pages 1-840 



Abbreviations, 831 

Absolute humidity, 8, 819 
Absolute pressure, 807, 819 
Absolute temperature, 819 
Absolute zero, 819 
Absorption, (sec also Regain) 
agents, 44 

as means of dehumidification, 492 
by building materials, 155 
of solar radiation by glass, 152 
of sound, 592 
system, 492, 493 
Acceleration, 819 

due to gravity, 819 
Acclimatization, 56 
Acoustics, acoustical, 583 

treatment, 591 
Activated alumina, 39 
Adiabatic saturation, 11, 495, 502, 819 

driers, 649 

Adjustable speed motor, 704, 709, 710 
Adsorption, 819 
agents, 37 

as means of dehumidification, 490 
systems 
alumina, 491 
silica gel, 491 
Air 

adiabatic saturation of, 11 
amount per person, 70 
atmospheric, 1 
changes of, indoors, 51, 129 
cleaning devices, 519, 819 
A.S.H.V.E. code for, 519 
requirements of, 519 
types of, 520 
composition of, 1, 51 
density of, 6 

distribution of, 72, 397, 547 
balancing, system, 560 
for comfort, 69 
effect of turning blades, 554 
factors in room cooling, 552 
factors in room heating, 554 
grille locations, 547 
natural ventilation, 669 
railway air conditioning, 560, 610 
residence, 397 

with unit air conditioners, 455 
with unit heaters, 441 
with unit ventilators, 446 
dry, 1, 4, 8, 59, 822 
drying agents, 35, 37 
ducts, 563, (see also Ducts, Air) 
excess, 168 
exfiltration, 121, 413 
filtration, 121, 180, 229, 413, 820 



Air (continue<f) 
flow, 72, 77 

control, principles of, 675 

formulae, 563 

into a hood, 638 

loudness chart, 556 

natural, measurement of, 678 

requirements, 676 

through openings, 670, 675 
friction of, in pipes, 567, 568 
impurities in, 79, 676 

size of, 80 
ionization of, 75 
leakage, 121, 127 

minimum outdoor, requirements, 7S 
mixtures with water vapor, 12 
moist, 68 
motion, 72, 74 

movement, measurement of, 811 
odors in, 51 
optimum conditions, 62 

indoors in summer, 68 
outlet noises, 554 
outside, introduced, 

fan systems, 414 

through cracks, 126, 129 

through doors, 127 

unit air conditioners, 455 

unit ventilators, 447 
pollution, 79 

abatement of, 84 

effect on health, 83 
primary, 167 
properties of, 3, 4 

for combustion, 167, 176 

for ventilation, 70, 609 
recirculation of, 77 

fan systems, 411, 417 

unit ventilators, 447 
saturated, 1, 5, 10, 827 
secondary, 167 
space conductances, 93 
speeds to convey material, 642 
standard, 828 
summer, conditions, 68 
still, 57 

synthetic chart, 829 
velocity, (see Velocity, Air) 
vitiation, 51 
volume, 12 
washer, 499, 820, (see also Washer, Air) 

operation of, 690 

saturation efficiency, 502 
weight of, 6 

Air conditioning 51, 503, 819, (see also Air) 
air change per occupant, 71 
chemical factors, 55, 81 
comfort chart, 63, 64 
in disease treatment, 597 



Vil 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Air conditionin 



, -V.7 

with, ice, V,,<} 



, 

tus for, .503 
automatic control. <83 
exhaust aystems, t>33 
operation cf, 485 
process conditions, G21 
unit coolers, 449 

objective of, 1 

physical factors, 51 

redrcalation, 77, 411. 417, 447 

symbola, 836 

units, 451 

Algae formations. 514 
Allergic disorders, 004 

classification of, 601 

treatment cf, 
apparatus for, 604 
limitations in, 605 
Alternating current motor, 703 
Altitude. 1S3 

Alumina system of adsorption, 30, 491 
Aluminum foil, 94 
Aluminum oxide, 39 
Ammonia, 35, 36, 511 
Anemometer, 812. 820 
Anesthesia, 597 

apparatus, 507 

effect of, 598 

inflammability, 598 
Anthracite, 165, 169, (see also Coal) 

stokers, 205 
Apartment bouses, 

hot water supply to, 797 

steam consumption, 234 

stokers suitable for, 206 
Appendicitis, 599 
Artheritis, 607 
A.S.H.V.E. Codes and Standards, 247. 281, 518, 

534. 680, 839 

A.S.M.E. boiler construction code, 257 
Artificial fever, 602 

conditions for, 603 

diseases treated, 603 

limits for. 603 

production of, 603 
Asbestos, 725 
Ash* 

cared for by stokers, 201 

fly, 79 

Asphyxia, 605 
Asthma, 604, 605 
Atelectasis, 605 
Atmosphere, standard, 807 
Atmospheric steam heating system, (see also 

Steam Heating Systems) 
Atmospheric water cooling apparatus, 507 

design of, 510, 511 

efficiency of, 512, 516 
Atomization, 

for humidifying. 504 

of 02, 214 
Attic fans. 464 

Automatic control, 399, 608. (see also Controls) 
Automatic fuel burning equipment, 201 
Awnings, 156, 406 
Arm! velocity formula, for hoods, 637 



B 



Babcock's formula for steam flow, 301, 766 

Baby care, (see Nurseries) 

Baffles, 595, 820 

Balancing air distribution system, 560 



Barn ventilation 679 
Barometer, 

aneroid. 808 

mercurial, 807 

Barometric pressure, 183, 807 
Baudelot, 

chamber, 502 

cooler, 496 

Bends, expansion, 362 
BET, British equivalent temperature, 356 
Biochemical reactions, control of, 628 
Bituminous coal, 165, 171 
Blast, 820 
Blower, blowers, 531, (see also Fans) 

standard test code for, 534 
Body, 

human, surface area, 71 

odors, 71 

Boiler, boilers, 243, 820 

allowances, 252, 802 

A.S.H.V.E. test codes, 248, 840 

A.S.M.E. construction code, 258 

baffles, 395, 820 

capacity, 243, 442 

care during summer, 261 

cast-iron, 243 

cleaning, 260 

codes, 248 

combustion rate, 244 

connections, 258, 316 

controls, 698 

conversion, 218, 256 

design of, 246 

domestic oil burners, 218 

draft loss through, 189 

efficiency of , 247, 251 m 

for electric steam heating, 745 

erection of, 259 

fittings, 258 

gas-fired, 222, 245, 256 

grate area, 255 

heat transfer rates, 247 

heating, surface, 247, 820 

horsepower, 251, 820 

installation, 256. 259 

insulation. 261 

limitations, 257 

low pressure, construction code, 258 

maintenance, 259 

oil burners, 4, 218 

operation, 259 

output, 250 

performance curves, 254 

pick up, 252 

pipe tax, 253 

ratings of, 248, 249 

run out sizes, 319 

scale in, 260 

selection of, 251, 254, 255 

settings, 218, 246 
for mechanical stokers, 211 

special. 245 

steel, 243 

troubles with, 260 

types of, 240 

warming-up allowance, 252, 254 

water line, 258 
Boiling point of water, 27 
Booster, 

coils, 411 

fans, 390, 426 
Booths, spray, 640 
Bourdon tube, 808 
Boyle's law, 7 

Brake horsepower, heat equivalent of, 141 
Breeching, draft loss through, 193 
Brine, 454, 483 

British equivalent temperature, 756 
British thermal unit, 820 
Building, buildings, 

absorption coefficients, 155 

air velocities in, 569 



ALPHABETICAL INDEX TO TECHNICAL DATA SECTION 



Building, buildings (continued) 

classification, for district heating, 777 

construction, heat transmission of, 91, 97 

district heating, 770 

fuel requirements of, 229 

hot water supply to, 794, 797 

intermittently cooled, 149 

intermittently heated, 141 

load factors, 240 

materials, heat transmission of, 97 

noise in, 5S7 

saving of steam in 771 

steam consumption, 234 

tall, infiltration in, 128 

water supply to, 783 
Burner, burners, 

automatic equipment, 201 

coal, 201 

conversion, 224 

gas, 221 

oil, 213 
By-pass method, 425, 820 



Cabinets, (see Enclosures) 
Calorie, 820 
Calorific values, 

coal, 166 

gas, 176 

oil, 174 

Capacitor motor, 706 
Capillary moisture, 651 
Carbon dioxide, 36 

concentration in air, 72 

as corrosion agent, 374 

as an Index of, 

combustion, 168, 176, 212, 220, 224 
draft loss, 192 
odors, 52 

measurement of 815 

as a refrigerant, 38 
Carbon monoxide, 

in air, 84 

in garages, 681 

produced by gas, 224 

produced by oil burners, 220 

produced by stokers, 212 
Carnot cycle, 475 

Cattle, heat and moisture produced by, 678 
Ceilings, heat transmission, 111 
Central air conditioning systems, 423 

classification of, 423 

cooling cycle control for, 691 

design of, 427 

location of apparatus, 428 

ratings of, 429 

spray type, 424 

zoning, 428 
Central fan heating systems, 409, 688, 820 

computations for 413 

design of, 413 

electrical, 744 

heating cycle control for, 688 

heating requirements of, 412 
Characteristics of motors, 708 
Charles* law, 7 

Chemical reactions, control of, 628 
Chimney, chimneys, 179 

areas of, 187, 189, 191 

characteristics, 182 

construction of, 195 

effect, 129, 670, 672 

for gas heating, 196 

gas temperature, 184 

performance, 186 

sizes, 187, 189, 191, 198 

Venturi, 180 



Chorea, 603 

Cleaners, air, (see Air, Cleaning Devices) 

Clearance, window sash, 124 

Climatic conditions, 138 

Coal, (see also Anthracite, Coke, Lignite) 

air speed for conveying, 642 

analysis of, 165 

bituminous, 165, 171 

burning rate chart, 238 

calorific value, 166 

classification of, 165 

dust, disposal of, 79 

dustless, 172 

pulverized, 172 

semi-bituminous, 165, 172 

size of, 169 
Coal burning systems, 

automatic control of, 699 

automatic firing equipment, 201 

boilers, 243 

combustion rate, 394 

draft required for, 192 

fuel requirements, calculation, 230 

furnace requirements, 395, 400 

hand-fired, 173 

stokers, 201 
Codes, 

A.S.H.V.E. codes and standards, 839 

for grinding, polishing, and buffing wheels, 636 

for proportioning warm air heating plants, 222 

for rating air conditioning equipment, 435, 462 

for use of refrigerants, 426 

Coefficients of heat transmission, (see Heat Trans- 
mission, Coefficients) 
Coils, 

booster, 411 

cooling, 406, 453 

evaporator, 406 

heating, 404, 411 

hot water, 404 

pipe. 323 

preheater, 411 

radiator, 263 

reheater, 411 

steam, 411 

tempering, 411 
Coke. 166, 210, 411 

combustion of, 172 
Cold, effects on human body, 55 
Collectors, dust, 643 
Column radiator, 821 
Combined system, 

air conditioning equipment, 423 

central fan, 409 
Combustion, 165 

air required for, 167, 168, 176 

constants, 659 

of different coals, 169, 171, 209 

in driers, 655 

of gas, 176, 224 

of oil, 219 

rates for heating boilers, 244 

smokeless, 247 

with various stokers, 209 
Comfort, 57 

chart, 64 

conditions of, 147 

effective temperature, 60, 61, 62 

heating for. 753 

level, 267 

line, 63. 66, 821 

for men working, 66 

optimum air conditions for, 62 

school children, 65 

zone, 62, 821, (see also Zone, Comfort) 
Compensated cooling control, 693 
Composition of water, 27 
Compound wound motor, 703 
Compressed air, 504 
Compressors, 470 

control of, 701 

reversed refrigeration 495, 749 

types of, 471 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Condensation, 

4>n balidin* surface*, 1*1 
metew, 773 

prevention of, 141, 734 
rate in radiators, 267 

return pumps, 2tal 

in steam beating systems, 275, 301 
Condenser, 48 1 

design data, 481, 511 

performance of, 481 

turbine, 507 

types cf, 481 

water temperatures, 511 
Conditioning and drying, 627, (s also Atr Condt- 

tionint) 
Conductance, 90, 92, 821 

of air maces, 90, 93 

of building materials, 97 

of insulation. 97, 723 

surf ace. 92 
Conduction, 263, 821 

drying by, 647 

beater. 742 

Conductivity, 90. 92. 821 
Conductor, 821 
Conduit, 707 

Constant relative humidity. 821 
Constant speed motor, 704, 70S, 709 
Constant temperature drier, 650 
Construction code for low pressure boilers, 258 
Contours, velocity, 637 
Control, controls, 683 821 

of air conditioning equipment. 485. 683, 688, 700 
combined system, 688 
split system. 689 

apparatus, 684 

automatic, 399. 683. 697. 698 
gas burner. 698 
oil burner, 698 
stoker, 699 

compensated cooling. 693 

of cooling; units. 695 

domestic hot water, 700 

of draft, 181 

of electric motors, 711 

electric system, 686 

of electrical heating. 750 

of fans, 541 

modulating, 687, 745 

moisture content. 625 

of natural ventilation, 399, 673 

of noise, 584 

of ofl burning; equipment, 698 

pneumatic system, 686 

positive acting, 686 

pressure, 685 

railway systems. 612, 613 

rate of biochemical reactions 628 

rate of chemical reaction, 628 

rate of crystallization, 629 
" " " " quipment, 701 



of refrigeration equi 
compressor, 701 



vacuum, 701 
weft water, 702 

of regain, 624 

of relative humidity, 685 

residential, systems, 699 

room, 687 

self-contained, system. 686 

of sound, 583 

of steam V^t*"g gys^rns, 291 

of temperature, 220, 683, 750 

types of, 686 

wut. 220.683, 750 

of vacuum pomps, 295 

rone, 291, 688 
Convection, 821 
Gosmctor*, 263, 268, 821 

A^H.V.E* code for, 271 

connections for, 322 

correction rating factors, 271 

design of, 269 

drying by. 649 



Convectors (continued) 

gravity, 263 

heat emission by, 270 

heating capacity. 270 . 

performance characteristics, 270 

selection, 270 
Conversion burners, 224 
Conversion equations, 833 
Coolers, 

surface, 431 

types of 483 

unit, 435, 449 
Cooling, 11, 24 

with central fan heating systems, 406, 423, 485 

design, system. 407, 427 

effect, 10 

effective temperatures for, 68 

by electric refrigeration, 470. 749 

equipment, design of, 507 

evaporative, 423, 483, 501 

of fluids, 511 

of human body, 147 

load, 147 

with mechanical warm air systems, 407 

methods, 406, 423, 469 

ponds, 512 

railway air conditioning, 411 

relative humidities for, 68 

spray, 469 

surface, 469 

towers, 482, 512 

units, thermostatic control, 695 

water, 507 
Copper pipe, 356 

heaUoss, 721 
Corrosion, 

of boilers, 261 

of industrial exhaust systems, 645 
protective materials, 646 

inhibitors, 375 

of pipe, 374 

tester, 375 
Costs, 

of attic fans, 460 

of district heating service, 778 

of railway air conditioning, 617 

of unit conditioners, 464 
Crack, window, 124 
Crystallization, control of, 629 
Cyclone dust collector, 643 



Dalton, law of partial pressures, 1 
Damper, dampers, 

apparatus which operates, 683 

control, 673 

in duct systems, 398 

motors, 685 

types of, 398 
Decibel, 583, 822 
Definitions, 68 
Defrosting coils, 450 
Degree-day, 822 

base temperature for, 234 

methods of estimating fuel consumption, 231 

records for cities, 232 
Degrees, perspiration, 73, 75 
Dehumidification, 11. 419, 469, 822 

by absorption. 492 

by adsorption, 490 

effective temperatures for, 66 

methods of, 423, 453, 490 

by refrigeration, 469 

relative humidities for, 68 
Dehumidifier, dehumidifiers, 169 

alumina, 491 

in central air conditioning systems, 424 

in industrial air conditioning, 503 

silica gel, 491 

types of, 453, 507 



ALPHABETICAL INDEX TO TECHNICAL DATA SECTION 



Density, 3, 822 

of air, 6 

of saturated vapor, 12 

specific, 3 

of water, 27 
Dennatitus, 604 

Design conditions in industrial conditioning, 621 
Design temperature, 

dry-bulb, 138, 147 

wet-bulb, 147, 511 
Dew-point, 822 

relation to relative humidity, 9 

temperature, 2 
Diameter, circular equivalents of rectangular 

ducts, 572 
Diarrhea, 600, 601 

Dichlorodifluoromethane, 35, 40, 473, 511 
Diffuser, 822 
Diphtheria, 52 
Direct current motor, 703 
Direct-indirect heating unit, 822 
Direct radiator, 822 
Direct return system, 332, 822 
Dirt pockets, 328 
Disc fans, test code for, 524 
Disease treatment, 

air conditions for, 599, 600, 603 

allergic disorders, 604 

anesthesia, 597 

artificial fever, 602 

classification of diseases, 602, 605 

diseases treated, 52, 599, 600, 603, 604, 605, 607 

explosion hazard, 597 

fever therapy, 602 

filtering in, 600 

hospital air conditioning, 597, 607 

nurseries, 600 

operating rooms, 597 

oxygen therapy, 605 

premature infants, 600 

satisfactory air conditions, 599, 600. 603 

sterilization of air, 650 

ventilation rates, 598, 602 

Distribution of air, 547, (see also Air, Distribution} 
District heating, 765 

building connections, 770 

conduits, 767 

economies in, 770 

meters, 774, 775 

pipe, (see also Piping} 
distribution, 765 
returns, 767 
sizing, 766 

rates, 778 

steam consumption, 777 

tunnels, 769 

Diverter, back draft, 196 
Domestic oil burners, 215 
Domestic stokers, 204 
Domestic supply, 

hot water, 747, 799 
control, 700 
load, 253 

water, 783 
Doors, 

air leakage through, 127 

coefficients of transmission of, 117 

natural ventilation through, 672 
Down-feed piping systems, (see Steam Healing 

Systems) 
Draft, 179 

available, 182, 186 

back, diverter, 196 
dimensions, 196 

calculations, 179 

capacity, 181 

control, 181 

equation, 187 



Draft (continued) 

mechanical, 180 

natural, 179 

requirements, 169 

theoretical, 182 
Drain connections, 259 
Drawing, symbols for, 836 
Drip, 822 

Dripping of steam pipes, 327 
Drum driers, 648 
Dry air, 822 

Dry-bulb temperature, (see Temperature, Dry-bulb) 
Dry return, 823 
Driers, 648, 649 

adiabatic, 649 

agitated, 648 

batch, 648 

compartment, 648 

continuous, 648 

cylinder, 648 

design, 658 

drum, 648 

festoon, 648 

high temperature, 663 

induction, 648 

intermittent, 648 

rotary, 648 

spray, 648 

tower, 648 

tunnel, 648 

vacuum, 648 
Drying, 627, 647, (see also Regain) 

adiabatic temperature, 649 

air circulation in, 653 

combustion, 655 

by conduction, 649 

constant temperature, 650 

by convection, 649 

design, 658 

direct contact, 649 

equipment for, 653 

estimating method, 665 

factors influencing, 651 

gas combustion constants for, 659 

high temperature, 652, 663 

humidity in, 652 

humidity chart, 654, 655 

industrial, 627, 647 

low temperature, 652 

mechanism of, 650 

methods of, 647 

moisture in, 651 

omissions in the cycle, 650 

by radiation, 647 

rules for, 652 

stages of moisture diffusion, 650 
constant rate period, 650 
falling rate period, 650 

sun, 647 

temperature in, 652 

time of, 653 
materials, 656 

ventilation phase, 661 
Duct, ducts 

air, 398, 563 
design of, 563 

equal friction method, 569, 575 
velocity method, 569 

for air distribution, 547 

air velocities in, 401, 642 

circular equivalents, 572 

construction details, 580, 641 

' ' of duct systems, 398, 569, 578, 634, 640, 



head, 822 

intensity required, 167, 190 

losses, 190 
in chimneys, 192 
through fuel bed, 190 



heat loss from, 732 
humidity measurement in, 814 
insulation of, 719, 732 
lining factor for sound, 592 
noise transmission through, 592 
pressure loss in, 564 

elbows, 564, 642 
for recirculated air, 381 
resistance, 643 
sheet metal for, 580, 642 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Duct, ducts coxiinutft 

suca of, 367, 571, 633 

temperature lose in, 415 

temperature measurement in, 809 

velocity measurement in, 811 
Duit, 7W, 823 

air speeds to convey, 635, 642 

catching devices, So 

collectors, 643 

concentration in air, 82, 815 

counter, SIo 

disposal of, SO 

Industrial exhaust systems, 633 

measurement cf, 815 

Dynamic equilibrium, Carrier's equation for, 2 
Dynamic head. 823 
Dysenterfa, 52 



E 



Eczema, 604 

EDR, equivalent direct radiation, 828 
Effective temperature, (see Temperature, Effective) 
Ether, 81, 579 
Elbow, elbows, 
design of. 367, 398 
equivalents, 340 
Ion of pressure in, 564 
resistance in, 643 
sheet metal used in, 641 
welding of. 368 
Electric, electrical, 
automatic, control system, 686 
central fan heating systems* 744 
control, motor, 703 
current, as corrosion agent, 374 
heat equivalent, 141, 160. 750 
heating, 741 
auxiliary, 749 
cost of .750 
of hot water, 747 
industrial, 748 
heaters, 742 
conduction, 742 
gravity convection, 743 
radiant, 743 
heating elements. 252, 742, 743 

with unit heaters, 743 
lamp bulbs, heat from, 160 
motors, 703 
resistors, 742 

Eliminator plates and baffles, 499 
Enthalpy, 22, 823 
Entropy, 473, 478, 823 

tables, 36, 38, 40, 42, 44 
Equations, conversion, 833 

dynamic. 2 

hygroscopic, 626 
Equipment noise, 586 
Equipment room, design of, 591 
Equivalent, equivalents, 

circular, 572 

direct radiation, 304, 601, 828 

tiljow, 340 

evaporation, 251, 823 

heat, 823 

of air infiltration, 140 
of brate horsepower. 141 
electrical, 833 
mechanical, 826 

length of run, 305 

square feet, 264 
Kitfimated design load, 823 
Estimated marmiTTTn load, 823 
Estimating driers, 665 
Estimating fuel consumption, 229 
Etfaytene. 567 
Eupatheoecope, 762, 817 



Evaporation, 516 
equivalent, 251 
from human body, 54, 74 
from water pans, 268 
Evaporative condensers, 483 
Evaporative cooling, 423, 483, 495, 501 
Evaporators, 483 
Exfiltration, 121, 229, 413 
Exhaust systems, 633 
classification of, 633 
collectors, 643 

corrosion, protection against, 645 
design procedure for, 634 
ducts for, 

construction of, 641 
design of. 640 
resistance in, 643, 644 
efficiency of, 645 
fans for, 645 
filters for, 644 
flexible, 640 
hoods for, 637 
air flow in, 638 

axial velocity formula for, 637 
chemical laboratory, 640 
large open, 639 
velocity contours in, 637 
industrial. 633 
lateral, 637 
motors for, 645 
spray booth, 640 
suction requirements, 635 
velocity requirements, 635, 642 
Expansion, 
of joints, 315, 767 
of pipe, 315, 359, 767 
in steam piping, 767 
tanks, 349 
Explosion hazard, 
inflammability of gases, 81 
in operating rooms, 597 
Exposure factors, 140 
Extended heating surface, 823 
Extended surface heating unit, 823 



F 



Fan, fans, 531 

A.S.H.V.E. test code for, 534 
attic, 464 

booster, equipment, 390, 426 
control of, 541 
designation of, 543 
drives, arrangement of, 542 
for drying, 540 
for dust collecting, 541, 645 
dynamic efficiency of, 533 
efficiency of, 533 
in electrical heaters, 744 
furnaces, 393 
for gas-fired furnaces, 222 
induced draft, 180 
for industrial exhaust systems, 645 
mechanical draft, 180 
mechanical efficiency of, 533 
motive power of, 543, 706 

control of, 703 

operating characteristics, 180, 533 
operating velocities. 539, 540 
performance of, 531, 539 
quietness of, 442 
ratings of, 538 

selection of, 396, 538, 541, 543, 645 
static efficiency of, 533 
system characteristics, 537 
systems of heating, 409 
tip speeds, 538 
total efficiency of, 533 
types of, 393, 531, 535, 539 
in unit conditioners, 455 
in warm air systems, 390, 396 



ALPHABETICAL INDEX TO TECHNICAL DATA SECTION 



Fatigue* human, 56 

Fever therapy, (see Artificial Fever) 

Filter, filters, 521 

automatic, 523 

cloth, 644 

design of, 521 

dry air, 524 

hay fever air, 604 

installation of, 525 

resistance of, 396 

for sound, 392 

unit type, 521 

viscous type, 521 
Fire walls, 640 
Firing rate, 169, 171 
Fittings, 355, (see also Connections, Pipe) 

areas of, 364 

boiler, 258 

copper, 365 

flanged, 366, 723 

lift, 287 

screwed, 364 

welding, 366, 370 
Flame, with oil burners, 214, 219 
Flanges, welding neck, 371, 372 

Flexible materials, 589 
Floors, heat transmission through, 111 
~~ is analysis, 816 
fluids, 
of, 511 

for flow of, 563 
774 

moisture of, 626 



gages, 




Force, 824 

Forced-air heating system, design, 3 

Forge shops, heat given off in, 675 

Formulae, 

conversion, 833 

heat transmission, 91 
Foundries, heat given off in, 675 



of cooling water, 517 

insulation against, 733 
Friction, 

of air, in pipes, 566, 567 

in chimneys, 185 

coefficients, 567 

factors, 393 

heads in pipes, 336 

in heating units, 412 

losses in ducts, 565, 567, 571 

in water pipes, 791 

Fuel, fuels, 165, (see also Anthracite, Coal, Coke, 
Gas, Lignite. Oil) 

bed. draft loss through, 189 

burning equipment, automatic, 201 

burning rate charts, 238 

consumption. 229, 236 

oil gages, 221 

oil, heating value, 174, 660 

oil specifications, 174 

requirements, 
of buildings, 236 
degree-day method. 231 
theoretical method, 230 

utilization of, 229 
Fumes, 79, 824 

industrial exhaust systems, 633 

toxicity of, 83 

Fundamentals of heating and air conditioning, 1 
Furnace, furnaces, 824 

capacity, 383 

design of, 173, 211, 246, 377, 383. 394, 400 

door slot openings, 486 

gas-fired, 222 

hand-fired, 173 

performance curves of, 385 

types of, 221, 393, 403 

volume, 824 

for warm air systems, 393 
Furnacestat, 399 



fuel oil, 221 

pressure, 824 

steam, 258 

vacuum, 808 
Galvanometer, 809 
Garage, garages, 

air flow necessary in, 676 

A.S.H.V.E. ventilation code, 679 

heaters, for, 224 
Gas, gases, 

burner control, 698 

burning rate chart, 239 

calorific value. 141, 176 
hi chimneys, 183 

combustion constants, 659 

constant for dry air, 8 

flue, analysis, 816 

fuel, 

manufactured. 176 
natural, 176 
properties of, 176 

inflammability, 81 

requirements per degree day, 237 

scrubbers, 86 

toxicity of, 83 
Gas-fired appliances, 221 

automatic control of, 225, 698 

boilers, 222, 245, 456 

carbon monoxide produced by, 224 

chimneys for, 196 

classification, 221 

combustion in, 224 

conditioning unit, 462 

control of, 225, 698 

conversion burners, 224 

furnace requirements for, 394, 900 

heat from, 160 

rate of gas consumption, 395 

ratings of, 226 

sizing, 225 

types of space heaters, 223 

used with unit heaters, 443 

warm air furnaces, 222 
Gaskets, 366 
Glass, 

heat transmitted through. 117, 152 

solar radiation through, 152 
Globe thermometer, 762 
Glossary of terms, 819 
Goitre, 599 
Gonorrhea, 603 
Grates, 824 

areas of, 249, 255, 383, 402, 421, 824 

of furnaces, 249, 255, 383, 402, 421 

of stokers, 201 
Gravity, 

circulation, 345 

converters, 263, 743 
heat emission of, 263 

gravity-indirect heating systems, 272 

pressure heads, 344 

specific, 3 

steam heating systems, 275, (see also Steam 
Heating Systems) 

warm air heating systems, design of, 377 
Grille, grilles, 824, (see also Registers) 

anemometer readings through, 812 

for concealed heaters, 270 

redrculating, 381 

of roof ventilators, 672 

velocity through, 401 

for warm air systems, 381, 397 



Hartford return connection, 258, 278, 318 

Hay fever, 604 

Hazard of explosion, in operating rooms, 597 



HEATING VEWTILATINO AIR CONDITIONING GUIDE 1938 



Health. Sd, 8!M, f see also Disease Treatment) 
Heart trouble, 605 
Heat, 824 

absorbed by bonding structure, 141 
of adsorption. 43 f M 

air infiltration equivalent of, 130 
capacity, 155, 823 

of leader pipe*, 378 
of condensation, 45 
conduction, 821 
consumption, 224 
content, 

of air and water vapor. 2 

of coal, 166 

of dry air. 22 

of gase*, 661 

of saturated water vapor, 23 
convection, 821 
conversion equations, 833 
demand, factors governing, 133, 241 
effects on human body, 54 
electrical equivalents of, 750, 834 

of convectors, 263, 270 

by radiation, 756 

of radiators, 263, 270 
equivalent, equivalents, 834 

of air infiltration, 130 

of brake horsepower. 140 

electrical, 350. 834 
exchanger. 507. 506 

shell and tube, 481 
flow meter, 817 
gain* 

from fixtures and machinery, 160 

for insulated pipe, 735 

from outside air, 158 

to be removed. 430 
infiltration equivalent of, 130 
latent, 31, 828, 

loss, 73, 76 
of the liquid, 28, 825 
loss, 

from bare pipe, 719, 721 

computation of, S9, 142, 750. 758 

cost of. 720 

determination of, 133, 140, 229, 753 

from ducts, 730 

effect of insulation on, 737 

from human body, 73, 753, 755 

by infiltration, 130, 229 

latent, 73, 76 

from piping of gas-fired furnaces, 225 

by radiation, 61, 753 

sensible, 73. 755 

to unbeated rooms, 118 

vtvntjfaf \nf\i 675 

mftTftTiiyp^ probable demand, 133, 241 

of mixing. 47 

Tru^f^r^fg] eQuivalent of, 826 
produced by cattle, 679 
produced by human body, 53 
pump, 472, 749 
radiant, 753 

calculation of, 758 

measurement of, 761 

types of. 756 
radiation, 743. 753 
regulation in p*?", 53, 57 
requirements, 229 
sensible, 147. 827 

of air, 12 

loss, 73, 756 

of water, 31 
solar, 151 
sources of, 745, 754 

other than heating plant, 140, 149 
specific, 31 
total, 22. 829 

of saturated steam, 28 
transfer, 89 

coefficients, 90 

rate, 247 



Heat (continued) 
transmission, 89, 754 
through air spaces, 91 
through building materials, 91 
calculations, 89 
coefficients, 89, 96 
of ceilings, 111 
combined, 118 
of copper pipe, 721 
of doors, 117 
of floors. 111 
of glass walls, 117 
of insulation, 97, 821 
of partition walls, 110 
of roofs, 114 
of skylights, 117 
of surface conductance, 92 
of walls, 104 
of windows, 117, 151 
convection equation, 754 
definition of terms used, 90 
effects of solar radiation on, 151 
formulae, 91 
through glass, 116, 151 
measurement of, 817 
in surface coolers, 431 
by surfaces not exposed to the sun, 149 
symbols used in formulae, 90 
tables, 89, 97 
through ducts, 730 
time lag, 155 
utilization, 229 
Heaters, 
direct-fired, 443 
for domestic hot water, 799 
electric, 741 
capacity of, 750 
conduction, 743 
convection, 743 
radiant, 223. 743 
space, 223 
unit. 437, 743 
wall, 222 

Heating, (see also Heaf) 
auxiliary, 749 
district, 765 
effect of radiators, 266 
electrical, 741 
elements, electric, 742 
fundamentals of, 1 
load, 133 
medium, 825 
radiant, 743, 753 
railway air conditioning, 611 
by reversed refrigeration, 472, 749 
surface, 247, 825 

square foot of, 828 
symbols, 836 
systems, 
district, 765 
electrical, 741 
fan, 409 

gravity warm air furnace, 377 
hot water, 331, 825 
mechanical warm air furnace, 393 
radiant, 743, 753 
steam, 275, 745 
units, 

blow-through, 411 
central fan, 744 
draw-through, 411 
value, fuel oil, 660 
water, 783 

Henry and Dalton, law of, 375 
Hoods, 

axial velocity formula, 637 
canopy, 639 

for chemical laboratories. 640 
design of, 634 
for exhaust systems. 637 
of furnaces, 395 
open, 639 

suction pressures at, 635 
velocity pressures at, 637 



ALPHABETICAL INDEX TO TECHNICAL DATA SECTION 



Horsepower, 825 
boiler, 251 

brake, heat equivalent of, 140 
Hospital air conditioning, (sec Disease Treat- 
ment) 

Hot box, 817 
Hot plate, 817 
Hot water, domestic 
control of, 700 
load, 253 
' supply, 797 
Hot water heaters, 245, 799 
Hot water heating systems, 331, 825 
electric, 720 

forced circulation, 331, 337 
gravity circulation, 331 
installation of, 351 
mechanical circulation, 333 
Hot water piping, 331 
Hotels, 

steam consumption, 234 
stokers suitable for, 201 
temperatures of, in winter, 134 
water supply, 783 
Humidificatfon, 10, 499, 825 
apparatus for, 503 
atomization for, 504 
effective temperatures for, 65 
methods of, 452 
relative humidities for, 68 
for residences, 403 
systems of, 503 
with washer, 501 
Humidifier, humidifiers, 466 
atomizing, 504 
with fan systems, 419 
high-duty, 504 
self-contained, 505 
spray, 505 
types of, 466, 503 
Humidistat, 400, 825 
Humidity, 8, 825 
absolute, 8, 819 
control, 685 

railway air conditioning, 612 
in drying, 652 
in hospitals, 597 

for industrial processing, 622, 623 
measurement of, 814 
optimum, 68 

relative, 9, 827, (see also Relative Humidity) 
in comfort zone, 63 
effect on moisture regain, 625 
relation to dew-point, 9 
specific, 8, 825 
Hygroscopic materials, 626 
moisture content, 625 
processing of, 627 
regain, 626 
Hygrostat, 825 
Hypertension, 607 
Hyperthyroidism, 607, 699 



Ice, in air conditioning, 407, 454, 496 

control of, 701 
Inch of water, 825 

Induction motor, 707, 710, (see also Motors) 
Industrial, 
air conditioning, 621 
apparatus for, 449, 503 
calculations, 629 
air pollution, 79 
control, 

biochemical reactions, 628 
chemical reactions, 628 
crystallization, 629 
moisture content, 625 
of regain, 624 



Industrial (continued) 

cooling systems, 469 

design conditions, 621 
drying, 540, 627 

electrical heating systems, 748 

exhaust systems, 633, (see also Exhaust Systems) 

general requirements, 624 

heat sources, 141 

temperatures and humidities for processing, 622, 
623 

unit heaters, 444 
Infants, premature, 63, 65, 600 
Infiltration, 121 

average, 126 

fuel utilization, 229 

heat equivalent, 130 

through shingles, 123 

through walls, 122 

through windows, 124 
Inflammability of gases, 81 
Institutions, water supply to, 804 
Instruments, 807 
[nsulation, 825 

asbestos type, 

corrugated, 725, 726 
laminated, 727, 728 

of boilers, 261 

bright metal foil, 94, 95 

building, 751 

characteristics of, 97, 723 

of conduits, 738 

of ducts, 732 

economical thickness, 736 

with electrical heating, 715 

heat transmission through, 97, 723 

for low temperatures, 733 

magnesia type, 724 

of piping, 719 

to prevent condensation, 141, 734 

to prevent freezing, 733 

reflective type, 94, 95 

rock wool type, 729 

of sound, 587 

tables, 97, 724 

thickness needed, 736 
underground, 737 
of vibration, 587 
lonization of air, 75 
Isobaric, 825 
Isothermal, 7, 826 



J-K 



Joints, expansion, 315, 767 
Kata thermometer, 811 



Lag in heat transmission, 155 
Latent heat, 31, 826 

loss, 72 

of water vapor, 12 
Lateral exhaust system, 637 
Leader pipes, 378 

heat carrying capacity of, 379 

size of, 379, 389 

Leakage of air, 121, (see also Infiltration) 
Lignite, 166 

Liquid, heat of the, 28, 825 

Lithium chloride system of adsorption, 46, 492, 493 
Load, 

building factors, 240 

cooling, 147 

design, 251, 823 

heating, 133 

hot water supply, 825 

maximum, 824 

radiation, 824 
Low temperature insulation, 733 



XV 



HEATING VENTHATINO AIR CONDITIONING GUIDE 1938 



M 



Machinery, 

as heat scarce. 140, 159 
mountings vibration, 587 
sound insulation of, 587 
Magnesia insulation, 724 
Manometer, 811, 826 
Manual control, (see Controls') 
Masonry materials, heat transmission through, 97 
Mass. 826 
Mb, 331, 826 
Mbh, 331, 820 

Mean radiant temperature, 754, 758 
Mechanical, 
draft towers, 515 
equivalent of heat. 82G, 834 
fuel burning equipment, 201 
refrigeration, 35 
ventilation, 77 

warm air furnace systems, 391 
air distribution, 397 
design of, 400 

register and grille locations, 397 
Medical treatment, (see Diseases) 
Mental trouble, 605 
Mercurial thermometer, 809 
Metabolism, 53, 73 
Meters, 
choice of .774 
condensation, 771 
fluid. 774 

NichoUs heat flow, 817 
steam flow, 776 
types of, 774 
water, disc, 789 
Methyl chloride, 37, 42, 511 
Metric units, 835 
Micromanometers, 808 
Micron, 79. 826 

Mixture, air and water vapor, 12 
Modulating control, 687 
Moisture, 
content, 

of air, 72, 147. 503, 625 
capillary or free, 651 
of hygroscopic materials, 626, 651 
loss by human body, 76 
from outside air, 158 
produced by cattle, 679 
regain. fi9o> 
Mol, 826 

Monitor openings, 672 
Monofluorotxichloromethane, 37, 44 
Motive power. 703 
Motors, electric, 703 
adjustable speed. 704, 709 
adjustable varying speed, 704 
alternating current, 705 
application of, 708 
capacitor type, 706 
characteristics of, 708 
classification of, 708 
compound round, 703 
constant speed, 704, 708 
control equipment for, 711 
automatic, 712 
manual, 711 
multispeed, 714 
pflot, 712 
single phase, 716 
slip ring, 715 
damper, 685 
direct current, 703 
control of, 713 

speed characteristics, 704, 708 
as heat source, 159 
induction, 

automatic start, 710 
capacitor start, 706 
repulsion, 705 
repulsion start, 707 
slip;ring -wound rotor, 710 
sQuirrd cage, 707 



Motors, electric (continued) 

polyphase, 707 

selection of, 645 

series wound, 703 

shunt wound, 703 

single phase. 706 

special applications, 711 

split phase, 707 

synchronous, 711 

varying speed, 705 
MRT, mean radiant temperature, 754, 758 



N 

Natural draft towers, 515 
Natural ventilation, 72, 669 
Nervous instability, 607 
Neurosyphilis, 603 
Nicholls heat flow meter, 817 
Noise, (see also Sound) 
air outlet, 554 
in buildings, 584, 587 
control of, 584 
through ducts, 592 
through room wall surface, 591 
with warm air systems, 396 
equipment, 586 
kinds of, 586 
level, 

acceptable, 585 
of compressors, 471 
of fans, 539 
of unit heaters, 442 
measurement of 584 
through building construction 587 
Nozzle, 499 
air spray, 499 
oil atomizer, 214 
water spray, 499 
Nurseries, 600 
equipment for, 602 
requirements for, 601 
ventilation rate, 602 



Odors, 69 

of human origin, 51 

concentration 70 

removed by outside air, 71 
Off peak heating, 748 
Oil, oils, 

atomization of, 507 
burner, burners, 

air for combustion, 214 

air supply for, 214, 219 

boilers, 216. 218 

burning rate chart, 238 

classification, 215 

combustion, 218 

for commercial use, 216 

control of, 220, 698 

design considerations, 219 

for domestic use, classification, 214 

efficiency of combustion, 220 

flame with, 214 

furnace requirements, 246, 394 

ignition, 214 

oil consumption, 229, 238 

operation, 214 

Orsat test, 220 

specifications, 173 

types of, 215 
calorific value of, 174 
classifications, 171 
as corrosion inhibitor, 375 
cost of, 175 
gages, 221 
ignition of, 174, 214 
preheating, 217 
specifications, 174 



ALPHABETICAL INDEX TO TECHNICAL DATA SECTION 



One-pipe steam heating systems, 275, 826 

Steam Heating Systems) 
Openings, 670 
air inlet, 672 
monitor, 672 . . 
for natural ventilation, 
location of, 675 
resistance offered to flow, 676 
size of, 669 
types of, 670 
Operating rooms, 
Anesthesia, 597 
explosion hazard, 597 
humidification, 598 
static electricity, 598 
ventilation. 598 
Orifice, orifices, 
friction heads, 612 



seam, 
Orsat test apparatus, 212, 220, 224, 816 
Outlets, (see also Registers, Grilles') 

design and location of, 559 
Oxygen, 375, 559 
Oxygen therapy, 

diseases treated, 605 

oxygen chambers, 606 

oxygen tents, 605 
Ozone, 77 



Paint, 

effect on radiators, 265 

soray booths, 640 

temperatures and humidities for processing, 623 
Panel radiation, 826 
Panel warming, 827 
Partial pressures, Dalton's law of, 1 
Perspiration, 51, 54, 73, 75 
Petterson-Palmauist apparatus, 815 
Pipe, piping, 355 

bare, heat loss from, 719 

bends, 315, 362 

capacities, (see Pipe, Sizes) 

coil radiators, 263 

conduit, 738, 767 

connections, 316, 770, (see also Connections) 

copper, 356 

corrosion, of, 374 

district steam, 765 . 

dimensions of, 359 (see also Pipe Sizes) 

expansion of, 315, 359, 767 

fittings, 364, (see also Connections, Fittings) 
for water supply, 788 
welding fittings, 366 

flanges, 370, 723 

flexibility of, 359 

freezing, 

prevention of, 733 

friction, 791 

of air in, 566, 567 
heads in, 336 

gaskets, 366 

hangers, 364 

heat loss from 225, 719 

for hot water heating systems, 331, 351 

insulation of, 719 

joints, 315, 769 

leaders, 378 

radiating surface, 722 

radiators, 263 

refrigerant, 484 

scale in, 374 

sizes, 

for boiler runouts, 318, 766 

for central fan systems, 323 

for convector connections, 322 

dimensions, 356, 359 

for district heating, 766 

for domestic hot water, 795 



Pipe, piping, sizes (continued) 
elbow equivalents, 340 
equivalent length of run, 305 
friction head, 337, 791 

of orifices in unions, 343 
for Hartford return connection, 318 
for hot water heating systems, 335 
for black iron, 337, 338 
for copper tube, 337, 339 
forced circulation systems, 337 
gravity circulation systems, 345 
for indirect heating units, 325 
mains, 790 

for pipe coil connections, 323 
for radiator connections, 320 
refrigerant, 484, 486 
return, capacity of, 308. 767 
steam, 302, 306, 307 
underground, 767 
tables. 306, 655 
tees, 364 

for underground steam, 767 
for water supply, 787 
weights, 361 
steam, capacity of, 304 
for steam heating systems, 275, 301, (see also 

Steam Heating Systems) 
supports, 364 
sweating, 734 
tax, 253 

tees, dimensions of, 367 
threads, 363, 365 
tunnels, 767 
types of, 355 
underground, 
insulation of, 737 
steam, 767 
for unit heaters, 442 
valves, 370 
water supply, 783 
weights of, 356 
welding, 366 

Pitot tube, 811 . . . . im 

Plastering materials, heat transmission through, 101 
Plenum, 

chamber, 827 nnn 

systems, automatic control of, 688 
Plumbing fixtures, 377 
Pneumatic control system, 286 
Pneumonia, 52, 599, 605, 607 
Pollen, 605 
Pollution of air, 83 
Polyphase motors, 707 
Ponds, cooling, 512 
Positive acting control, 686 
Post-operative pneumonia, 599 
Potassium permanganate, 514 
Potentiometer, 827 
Power, 827 

conversion equations, 833 
electric, 750 
supply for controls, 686 

Precipitators, dust, 527 
Premature infants, 600 

humidity of, 601 

mortality of, 602 

requirements of, 601 
Pressure, pressures, 

absolute, 819 

air 

in heating unit, 412 
measurement of, 811 

atmospheric, 807, 820 

for atomization, 504 

automatic control, 685 

barometric, 183, 807 

basic, 3 

controllers, 685 

conversion equations, 833 

drop, 566, 791 

drop through refrigerant pipe, 486 

dynamic. 823 



loss throug 



r pipe, 339, 486 
ducts, 563, 643 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Pressure, pressure \.& 



i , 

jurtial, Da I ton* a law of, 1 
rcfnxeratintf piant, 4S*t> 
of saturated vapor, 12 
static, 421, 82$ 
steam, 

in direct beating, 760 
drop, 278, 302, 307 
initial, 302 

in oriiice systems, 290 
saturated, 28 

in sub-atmospheric systems, 2S9 
total, 829 
vapor, 31, 830 
velocity, 83O 
water, 27, 789 
Prime surface, 827 
Processing, 621 

cooling systems, 469, 621 . 

industrial, temperatures and humidities for, 622 
of textiles, 626 
unit heaters, 444 
Propeller fans, test code for, 534 
Psychrometer, 827 

sling, 811 
Psycfarometric, 
chart, 25, 60, 61, 62, (back ewer) 
for drier, 654 
explanation, 25 
tests, 59 

Pulmonary disturbances, 605 
Pump, pumps, 
centrifugal, 334 
characteristics, 181 
circulating, 333 
condensation return, 292 
heat, 472, 749 
vacuum, 293 
Pyrometer, 810, 827 
mercurial. 810 
optical, 810 
radiation, 810 
thermo-electric, S10 



0-R 

Quality, 

of air, 69, 70, 71 

impaired by rerirculation 83 
Quantity, 

of air, 

measurement of, 811 

necessary for ventilation, 70. 71, 72, 158, 
609, 675 

of cooling water, 511 
Radiant heaters, 743 
Radiant heating, 753 

physical and physiological factors, 753 
Radiation, 827 

by black body, 759 

drying with, 647 

equivalent direct, 304, 828 

heat loss by, 63, 76, 754 

by human body, 63, 76, 754 

load, 252 

ofjwpe,722 

by radiators, 263 

solar. 151, (see also Solar Heat) 
occlusion of , 84 
through glass, 152 
through walls, 152 

ultra-violet. 75, 82 
Radiator, radiators, 263, 827 

A^,H.V.E. code for, 271 

column, 821 

concealed, 821 

condensation rate in, 267 

connections. 320, 348 

control of, 687 

correction rating factors, 271 

effect of saperheated steam, 265 

enclosed, 267 

gas-fired, 223 



Radiator, radiators (continued) 
heat emission of, 263, 270 
heating capacity of, 270 
heating effect of, 266 
for hot water systems, 346 
output of, 264 
paint, effect of, 265 
panel, 827 
pipe coil, 203 
ratings of, 264 
recessed, 827 
selection, 270 
tube, 829 
types of, 263 
wall, output, 264 
warm air, 223 

Railway air conditioning, 609 
air distribution, 560, 610 
cleaning, 611 
cooling equipment, 611 

calculation of, load, 619 

capacity, 612 
costs, 617 
heating, 611 
humidity control, 612 
power requirements, 613 

tractive resistance, 615 
temperature control, 613 
ventilation, 609 
Raoults law, 493 
Receivers, alternating, 299 
Refrigerants, 35, 827 
ammonia, 36 
carbon dioxide, 38 
codes for use of, 426 
dichlorodifluoromethane, 40 
lithium chloride, 46, 47 
methyl chloride, 42 
monofluorotrichlorometbane, 44 
water, 45 

Refrigerating, capacity, 429, 475 
Refrigerating plant, 24, 469 
centrifugal, 478 
compressor, 470, 512 
operating methods, 485 
size of, 429, 475. 485 
steam jet system, 477, 512 
types of, 471 
Refrigeration, 
characteristics, 481 

curves, 480, 481 
coefficient of performance, 475 

carnot cycle, 475 
compression ratio, 477 
control of, equipment, 701 
dehumidification by, 470 
efficiency, 

cycle, 475 

ejector, 479 

mechanical, 477 . 
losses. 476 
mechanical, 472 
pipe sizing, 484 

discharge, 486 

liquid, 487 

suction, 488 
practical cycle, 475 
reverse cycle, 749 

limiting factors, 749 
systems, 

absorption, dosed, 493 

centrifugal, 479 

mechanical, 496 

steam ejector, 477 

various types, 469 
theoretical mechanical cycle, 473 
theoretical work per pound, 474 
ton of, 429, 475, 829 
ton days of, 829 
unit of, 429, 475 
Regain, 
control of, 624 
of hygroscopic materials, 626 
Registers, 827, (see also Grilles) 
with gas-fired furnaces, 223 
with gravity furnace systems, 381 



ALPHABETICAL INDEX TO TECHNICAL DATA SECTION 



Registers (.continued') . 
with mechanical warm air furnace systems, 397 
selection of, 381 
sizes, 381, 389 
temperature, 401 
velocity through, 401 
Reheater, 424, 432 
Relative humidity, 9, 826 
apparatus sensitive to, 684 
in comfort zone, 64, 68 

relation of dew-point to, 9 
control of, 684 
in industrial plants, 622, 624 
for processing, 622 
in public buildings, 67 
in residences, 403 
from water pans, 403 
Relays, 685 
Relief valves, 350 
Repulsion motors, 706, 707 
Research residence, 388, 406 
Residences, 

air distribution in, 397 
automatic fuel burning equipment, 201 
conditioning units, 291, 460 
control systems, 399, 699 
gas heat, 221 
humidification of, 403 
oil burners for, 213 
requirements in, 405 
steam consumption, 234 
stokers for, 204 
Resistance, 

of bright metallic surfaces, 94 
of building materials, 97 
in ducts, 565, 643 
of exhaust systems, 643 
of niters, 396 
of insulators, 97 
thermal, 829 
thermometer, 810 
Resistor, 742 
Respiratory diseases, 607 
Restaurants, 
tobacco smoke, in, 70 
water supply to, 804 
Return, 
dry, 823 
mains, 827 
pipe, capacity, 308 

Reverse cycle of refrigeration, 495, 749 
Reversed return system, 332 
Reynolds number, 184 
Ringelmann chart, 816 
Rock wool insulation, 100, 729 
Roof, roofs, f , 

coefficients of transmission of, 114 

conductivities of, 101 

solar radiation on, 152, 153, 154 

ventilator, 672, 827 

Room absorption correction charts, 557 
Room control, 687 



S 

Salts in cooling water, 509 
Saturated air, 827 
Saturation, fiber point, 651 
Scale, 

in boilers, 260 

Centigrade, 809 

on equipment, 509 

Fahrenheit, 809 

in pipe, 374 

Reaumur, 809 
School, schools, 

air flow necessary in, 70 

optimum air conditions, 65 

stokers suitable for, 201 

temperature of, in winter, 134 

ventilation in, 70 
Scrubbers, 499, 528 



Self-contained control system, 686 
Sensible heat, 147, 827 
of air, 12 
loss, 73 
of water, 31 

Series wound motor, 703 
Service connections, 770 
Sheet metal, for ducts, 580, 641 
Shingles air leakage through, 123 
Shunt wound motor, 703 
Skin diseases, 607 
Silica gel 

with oxygen chambers, 606 
regain of moisture of, 626 
silicon dioxide, 41 

equilibrium conditions, 43 
system of adsorption, 39, 41, 491 
Single phase motor, 706 
Sizes of pipe, (see Pipe Sizes) 
Skylights, 117, 671 
Sling psychrometer, 814 
Slip-ring wound motors, 710 
Smoke, 79, 827 
abatement of, 84 
measurement of, 816 
recorders, 816 
tobacco, 70 
Smokeless arch, 828 
Solar heat, 151 
absorption coefficients, 155 
effect of, 
awnings, 155 
latitude, 152 
intensity chart, 150 
occlusion of, 84 
radiation, 
factors, 154 
through glass, 152 
through walls. 152 
time lag, 155 
Solenoid valves, 685 
Sound, 583, (see also Noise) 
absorption coefficients, 589 
control, 583 
duct lining factor, 593 
effect on duct design, 567 
insulation of, 589 
intensity, 335 
measurement of, 584 
in steam heating systems, 303 
unit of, 583 
Specific density, 3 
Specific gravity, 2, 828 

of fuel gas, 176 
Specific heat, 3, 828 
of air, 5 

mean, of water vapor, 3 
of water, 31 
Specific humidity, 8 
Specific volume, 3, 828 

of saturated steam, 31 
Split phase motor, 707 
Split system, 828 
air conditioning equipment, 461 

automatic control of, 689 
central fan, 409 
unit ventilators, 445 

P booths for painting, 640 



wiuls. 513 

efficiency of, 512 
towers, 514 
distribution of, 504 
generation of, 504 
humidifiers, 505 

type of central station system, 423 
water coolers, 482, 512 
Square foot of heating surface, 828 
Squirrel cage motors, 707 
Stack, stacks, 378, 689 
effect, 670 

* 675 



wall, 380 
Stairways, 129 



HEATING VENTHJITING AIR CONDITIONING GUIDE 1938 



Standards, 
air, 82fe 

air conditioning, 51 

A.S.H.V.E. codes and standards, 248, 271, 839 
for fuel oil, 173 
for pipe, 350 
for radiators. 271 
for welding, 368 
Static pressure, 828 
Steam, 828 
coils, 452 

condensing rates, 266 
consumption for buildings, 234 
flow, Babcock's formula, 502 
heat content of, 23 
heating systems, 275, 828 

air-vent, 276, 270. 309, 310 

atmospheric, 283, 313, 321 

classification, 275 

condensation return pumps, 292 

connections, (see Connections, Fittings) 

corrosion of, 374 

design of, 275, 301 

dirt pockets, 328 

district heating, 765 

dripping of, 327 

electric, 745 

equivalent length of run. 305 

gravity systems, 275 

one-pipe, 275, 270, 309, 321 
two-pipe, 279, 310, 321 

with high-pressure steam, 313 

mechanical, 275 

orifice, 200, 303, 313, 321 

pipe, 301. (set also Pip*) 



sizes,* 

pressure drop in. 278 

sub-atmospheric, 287, 293, 303, 313, 321 

types of, 275 

vacuum, 285, 293, 295, 312, 830 

vapor, 303, 321, 830 
one-pipe, 280, 826 
two-pipe, 281, 282, 311, 829 

water hammer in, 303 

zone control, 291 
high pressure, 313 
jet apparatus, 477 
meters for, 774 
pressure, 313 
properties of, 28 

requirements of buildings, 234, 777 
saturated, properties of, 31 
savings in use of, 770 
superheated, 265, 828 

trap, 828 
tunnels, 769 
underground, 767 
in unit heaters, 440 
Sterilization of air, 600 
Stokers, 

apartment house, 206 
automatic control of. 399, 699 
classes of , 204 
combustion process, 209 

adjustments. 212 

efficiency, 212 
commercial, 206. 208 
controls, 213 
design of, 201 
economy, 201 
household, 204 
mechanical, 201 
operating requirements, 205 
overfeed flat grate, 201 
overfeed inclined grate, 202 
heating boilers, setting heights, 211 
types of, 201 

underfeed, 201, 829 

underfeed rear cleaning, 203 

underfeed side cleaning, 202 

of hoi water, 798, SQ2 
temperatures and humidities for,622 



Storm sash, 125 

Streptococcus, 52 

Stroke, heat, 599 

Sub-atmospheric systems, (see also Steam Healing 

Systems) 
Suction, 

static in exhaust systems, 635 
Summer, 

care of heating boilers, 261 

comfort zone, 64, 66 

conditioning, apparatus for, 423, 451, 499 

desirable indoor conditions in, 66 

wind velocities and directions, 148 
Sun, 

effect on heating requirements, 291 

factor of cooling load, 151 
Supply outlets, 

selection of, 381 

types of, 389 
Surface, 

conductance, 828 

cooling, 431 
equipment, 431 
air conditioning, 423 
ratings, 429 

extended, gravity-indirect heating systems, 272 

heating, 829 
square foot of, 828 

radiant heating, 759 
Sweating of pipe, 734 
Swimming pool, 804 
Symbols, 

for drawings, 836 

for heat transmission formulae, 90 
Synchronous motor, 711 
Synthetic air chart, 829 
Systems of control, 686 



Tank, tanks, 

for domestic water supply, 798, 802 

expansion, 349 

flush, 790 

Tees, dimensions of, 367 
Temperature, 

absolute. 819 

of air leaving outlets, 428, 549 

apparatus sensitive to, 684, 819 

atmospheric, 184 

of barns, 697 

base, for degree-day, 231, 234, 235 

basic, 3 

body, 53, 54. 754 

changes, effect on human beings, 55 

of chimney gases 184 

in cities, 138, 148, 232 

of city water main, maximum, 508 

control of, 213, 220, 225, 684, 750 
railway air conditioning, 613 

of cooling water, 482 

dew-point, 3, 822 

difference, 

between floor and ceiling, 136, 226, 439 
desired, determination of, 674 
in stacks and leaders. 378. 673 

dry-bulb, 2, 68, 823 
maximum design, 148 
specified in winter, 134 

for drying, 652 

effect on moisture regain, 622 

effective, 58, 68, 135, 147, 823 
chart, 58, 60, 61, 62, 64 
for maximum comfort, 64, 756 

optimum, 62 

scale, 59 



of gas flame, 176 
in industrial ] 



I processing, 722, 723 

inside, 63. 64, 134, 412 

surfaces, 758 
low, insulation for, 723 
of mean ulterior surface, 758 



ALPHABETICAL INDEX TO TECHNICAL DATA SECTION 



Temperature (continued) 

mean radiant, 754, 758 

measurement of, 679, 683, 809 

in occupied space, 68 

outside, 136, 148 

radiation-convection, 762 

range of cooling equipment, 511 

records of cities, 138, 148 

at registers, 428, 649 

room, 10, 231, 820 

sensations, 57 

surface, 
of man, 755 
mean interior, 758 

systems for control of, 213, 220, 225, 684, 750 

thermo-equivalent conditions, 59 

water main, maximum, 508 

of well water, 506 

wet-bulb, 11, 814, 830 
average, 511 
design, 147, 511 
as index of air distribution, 72 
maximum, 511 
Terminology, 819 
Test codes, 248 
Test instruments, 807 
Test methods, 807 
Textile, textiles, 

fibers, regain of moisture, 621 

temperatures and humidities for processing, 623 
Theaters, temperatures of, 67, 134 
Therm, 829 

Thermal resistance, 829 
Thermal resistivity, 829 
Thermocouples, 807 
Thermodynamics, 829 

of air conditioning, 1 

laws of, 826 

Thermo-equivalent conditions, 59 
Thermometer, 809, 810, 811 
Thermocouple, 809 
Thermopile, 810 
Thermostat, thermostats, 684, 829 

differential, 10, 683 

with gas-fired furnaces, 225 

immersion, 684 

insersion, 684 

location of, 399 

with oil burners, 220 

pilot, 690 

with radiant heaters, 750 

room, 684 

surface, 684 

types of, 673, 684 
Time lag, 155 
Tobacco smoke, 70 
Ton of refrigeration, 475, 829 
Ton-day of refrigeration, 829 
Total heat, 829 
Total pressure, 829 
Towers, cooling, 482, 512, 514, 515 

return, automatic, 298, 299 

with steam heating systems, 281, 295 

types of, 295 
Tube, 

Bourdon, 808 

Pitot, 811 

shell and tube heat exchanger, 483 
Tuberculosis, 83, 608 
Tubing, copper or brass, 365 
Tunnels, for steam pipe, 769 
Turbines, with unit heaters, 444 
Two-pipe steam heating systems, (see also Steam 

Heating Systems) 
Two position controls, 686 
Typhosus, 52 



Ultra-violet light, 75, 84 
Underfeed distribution system, 829 
Underfeed stoker, 229 
Underground piping, 767 



Underwriters' loop, 276, 318 

Unit air conditioners, 435, 451, 829 

air distribution, 455 

classification, 436 

controls for, 466 

cooling, 453 

dehumidification, 453 

filtering, 454 

heating, 452 

humidifying, 452 

location of, 455 

residential, 460 

types of, 436, 456 
Unit coolers, 435, 449 

control of, 695 

design of, 450 

frost removal from, 450 
Unit equipment, 435 

advantages, 435 

controls, 694 

miscellaneous, 464 
Unit heaters, 435, 744, 829 

air temperatures, 439 

control of, 695 

direction of discharge, 441 

piping connections, 442 

ratings of, 441 
Unit ventilators, 435, 444, 445, 446, 447, 829 

control of, 696, 830 
Unwin pressure drop formula, 766 
Up-feed piping systems, 275, 830, (see also Steam 

Heating Systems) 



Vacuum gage, 808 
Vacuum pumps, 292 
Vacuum refrigeration, 477 

control of, 701 
Vacuum system of steam heating, (see also Steam 

Heating Systems) 
Valve, valves, 370 

apparatus which operates, 683 

on boilers, 258, 316 

connections for, 770 

control, 685 
with steam heating systems, 315, 370 

with high pressure steam, 313 

pressure-reducing, 314, 770 
ratings of, 313 

for radiators, 277, 581 

relief, 350 

roughing-in dimensions, 373 

solenoid, 685 

sub-atmospheric system, 587 

on traps, 596 

types of, 370 

for water supply, 788 
Velocity, 830 

81 m ducts of buildings, 401, 569, 579 

in exhaust systems, 635, 642 
through heating units, 411 

measurement of, 811 
*i openings, 698 
sU towers, 515 

sound effect of, 579 
chimney gas, 187 

draft loss, 192 
contours, 637 

in ducts, 401, 635, 642, 811 
of fans, 539 
head, of fluids, 563 
meter, 813 
steam, 

through an orifice. 313 

in underground pipes. 765 
water, in pipes, 336, 338, 339 
wind, 

choosing, 126 

measurement of, 678 

on natural draft equipment, 515 

in natural ventilation, 669 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



\Vnt, vents, 
on traps, 2$C 
in unit ventilators, 446 

Ventilation, 51, 609, 830, (see also Air Dis- 
tribution) 
of barns, 679 
in drying, Ml 
of Ranges, 680 
in hospitals, 598, 902 
mechanical, 77 

with roof ventilators, 672 
natural, 77 

air changes per hour, 127 

control of, 073 

general rules for, 677 

heat to be removed by. 675 
openings, 

doors, *57I 

formula to determine size of, 009 

location of, 675 

skylights, 671 

types of, 670 

windows, 671 

for public buildings, 70, 575 
purpose of, 675 

quantity of air necessary for, 70 
railway air conditioning, 609 
by registers, 673 
for schools, 70 
by stacks, 670, 673 
symbols, 836 
Ventilator, ventilators, 
resistance of, 672 
roof. 672, 827 

unit, 235, (see also Unit Ventilators} 
Venturi chimney, 180 
Vibration of machine mountings, 587 
Vitiation of air, 51 
Volume, 

of air and saturated vapor, 12 
conversion equations, 834 
furnace, 824 
specific, 3 

of saturated steam, 28 
of water, 27 



W-Z 

Wall, walls. 

absorption of heat. 155 

ah- leakage through, 122 

of chimneys, 195 

condensation on r 141 

fire, 640 

heat transmission coefficients for, 89. 90, 97, 104, 
106, 108 

radiators, output, 264 

solar radiation on, 152, 153 

time lag through, 155 
Warm air heating systems, 830 

gas-fired furnaces for, 222 

gravity, 377 

mechanical, 393 

Washers, air, 396, 49ft, 524, 525, 820 
Water, 

boiling point of, 27 

circulating, temperature of, 512. 724 

from city main*, 482, 508 

cooling, 

eojoipment, 507 
quantity. 509 
temperature, 606, 508 

composition of , 27 

demand, 785, 804 

density of, 27 

domestic supply, 783, 797 

evaporation of. 516 

factor of usage, 785, 804 

flow from fixtures, 784, 785 

freezing, 733 

friction losses through pipes, 791 

hammer, 303 

heaters, 411, 799 

heating, 783 



Water (continued) 
hot, 

domestic supply, 783, 797 
boilers, 799 
demand for, 803 
electric heating of, 747 
pipe sizes for, 798 
storage of, 798, 802 

heating systems, 331, (see also Hot Water Heat- 
ing Systems') 
indies of water, 825 
line, 

in boilers, 258, 259, 275 
in water supply systems, 790 
make-up, 516 
meters, disc, 789 
pans, for humidification, 403 
pipe, 787 
pressures, 27 
probable usage, 785, 804 
properties of, 27 
as a refrigerant, 37, 45 
replacement of, 516 
supply piping, 783 
down-feed systems, 786 
mains, 790 
up-feed systems, 788 
temperature, maximum main, 508 

from wells, 506 
thermal properties of, 27 
vapor, 5, 10, 12 

given off in combustion of gas, 175 
heat content, 12, 23 
mean specific heat of, 3 
weight of saturated, 12 
Weatherstripping, 126 
Weight, 
of air, 6 

conversion equations, 834 
of steam, 28 
of vapor, 12 
of water, 27 
Welding, 355, 366 

neck flanges, 371, 372 
Well water refrigeration control of, 702 
Well water temperature, 506 
WeUbulb temperature, (see Temperature, Wet-bulb) 
Wet return, 830 
Wind, 

in cities, 138, 148 

effect on heating requirements, 137 
forces in natural ventilation, 121, 669, 675 
prevailing, direction of, 127, 148 
records of velocity and direction, 138, 148 
velocity on natural draft equipment, 515 
average, 127, 137, 148, 669 
equivalent, hi tall buildings, 128 
used in calculations, 127 
Window, windows, 671, 673 
air leakage through, 124, 126 
clearance of sash, 125 
coefficients of transmission of, 117 
comparison of various shades for, 156 
crack, 124 

measurement of, 124 
solar radiation through, 152 
storm sash, 125 
Winter, 

comfort zone, 63, 64 
conditioning, apparatus for, 393, 409 
cooling in, 147 
humidification in, 63, 68, 403 
inside temperature, 134 
relative humidity in, 68 
temperatures, 138 
wind velocities and directions, 138 
Zero, absolute, 819 
Zone, zoning, 

"for air conditioning systems, 428 
automatic control, 688 
comfort, 63, 64, 66, 821 
control of steam heating systems, 291 
for large heating systems, 351 
neutral, 826 
water supply systems, 783 



HEATING VENTILATING 
AIR CONDITIONING 





Vol. 16 v 1938 

Chapter 1 

AIR, WATER AND STEAM 

Dalton's Law, Temperatures, Air Properties, Humidity, Rela- 
tive Humidity, Specific Humidity, Relation of Dew Point to 
Relative Humidity, Adiabatic Saturation of Air, Total Heat 
and Heat Content, Enthalpy, Psychrometric Chart, Properties 
o Water, Properties of Steam, Rate of Evaporation 

A IR conditioning has for its objective the supplying and maintaining, 
,/JL in a room or other enclosure, of an atmosphere having a composition, 
temperature, humidity, and motion which will produce desired effects 
ugon the occupants of the room or upon materials stored or handled in it. 

Dry air is a mechanical mixture of gases composed, in percentage of 
volume, as follows 1 : nitrogen 78.03, oxygen 20.99, argon 0.94, carbon 
dioxide 0.03, and small amounts of hydrogen and other gases. 
- j ^Atmospheric air at sea level is given in percentage by volume as: N 2 
77.08, O 2 20.75, water vapor 1.2, A 0.93, C0 2 0.03 and H ? 0.01. The 
amount of water vapor varies greatly under different conditions and is 
frequently one of the most important constituents since it affects bodily 
comfort and greatly affects all kinds of hygroscopic materials. 

DALTON'S LAW 

A mixture of dry gases and water vapor, such as atmospheric air, obeys 
Dalton's Law of Partial Pressures; each gas or vapor in a mixture, at a 
given temperature, contributes to the observed pressure the same amount 
that it would have exerted by itself at the same temperature had no other 
gas or vapor been present. If p = the observed pressure of the mixture 

international Critical Tables. 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

and pi, fa, pt, etc. = the pressure of the gases or vapors corresponding to 
the observed temperature, then 

P-#i + fc + />a, etc. (1) 

TEMPERATURES 

Air is said to be saturated at a given temperature when the water vapor 
mixed with the air is in the dry saturated condition or, what is the equiva- 
lent, when the space occupied by the mixture holds the maximum pos- 
sible weight of water vapor at that temperature. If the water vapor 
mixed with the dry air is superheated, i.e., if its temperature is above the 
temperature of saturation for the actual water vapor partial pressure, the 
air is not saturated. 

The starting point of most applications of thermodynamic principles to 
air conditioning problems is the experimental determination of the dry- 
bulb and wet-bulb temperatures, and sometimes the barometric pressure. 

The dry-bulb temperature of the air is the temperature indicated by any 
type of thermometer not affected by the water vapor content or relative 
humidity of the air. The wet-bulb temperature is determined by a thermo- 
meter with its bulb encased in a fine mesh fabric bag moistened with clean 
water and whirled through the air until the thermometer assumes a 
steady temperature. This steady temperature is the result of a dynamic 
equilibrium between the rate at which heat is transferred from the air to 
the water on the bulb and the rate at which this heat is utilized in evapora- 
ting moisture from the bulb. The rate at which heat is transferred from 
the air to the water is substantially proportional to the wet-bulb depres- 
sion (t / l ), while the rate of heat utilization in evaporation is propor- 
tional to the difference between the saturation pressure of the water at 
the wet-bulb temperature and the actual partial pressure of the water 
vapor in the air (e } e). Carrier's equation for this dynamic equilibrium 
is 

1-c B -j 

t - /' 2800 - 1.3*' 

In the form commonly used, 



where 

e actual partial pressure of water vapor in the air, inches of mercury. 
c 1 = saturation pressure at wet-bulb temperature, inches of mercury. 
B = barometric pressure, inches of mercury. 

/ = dry-bulb temperature, degrees Fahrenheit. 
t* = wet-bulb temperature, degrees Fahrenheit. 

Formula 2b may be used to determine the actual partial pressure of the 
water vapor in a dry air-water vapor mixture. Then, from Dalton's Law 
of Partial Pressures, Equation 1, it follows that the partial pressure of the 
dry air is (B - e). 

If a mixture of dry air and water vapor, initially unsaturated, be cooled 



CHAPTER 1. AIR, WATER AND STEAM 



at constant pressure, the temperature at which condensation of the water 
vapor begins is called the dew-point temperature. Clearly the dew-point 
is the saturation temperature corresponding to the actual partial pressure, 
e, of the water vapor in the mixture. 

AIR PROPERTIES 

Density is variously defined as the mass per unit of volume, the weight 
per unit of volume, or the ratio of the mass, or weight, of a given volume 
of a substance to the mass, or weight, of an equal volume of some other 
substance such as water or air under standard conditions of temperature 
and pressure. The term specific gravity is more commonly used to express 
the latter relation but, when the gram is taken as the unit of mass and the 
cubic centimeter as the unit of volume, density and specific gravity have 
the same meaning. The term specific density is sometimes used to dis- 
tinguish the weight in pounds per cubic foot; and as here used, density is 
the weight in pounds of one cubic foot of a substance. 

The density of air decreases with increase in temperature when under 
constant pressure. The density of dry air at 70 F and under standard 
atmospheric pressure (29.921 in. of Hg) is approximately 0.075 Ib (see 
Table 1), while that of a mixture of air and saturated water vapor at the 
same temperature and barometric pressure is only about 0.0742 Ib. In 
the mixture the density of the dry air is 0.07307 and that of the vapor is 
0.00115 Ib (see Table 2). 

In order to make comparisons of air volumes or velocities it is necessary 
to reduce the observations to a common pressure and temperature basis. 
The basic pressure is usually taken as 29.921 in. of Hg, but no basic tem- 
perature is universally recognized. Common temperatures for this 
purpose are 32 F, 60 F, 68 F, and 70 F. Since 70 F is the most commonly 
specified temperature to which rooms for human occupancy must be 
heated, it is usually understood, when no other temperature is specified, 
that 70 F is the basic temperature for measuring the volume or the 
velocity of air in heating and ventilating work. 

The specific volume of air is the volume in cubic feet occupied by one 
pound of the air. Under constant pressure the specific volume varies 
inversely as the density and directly as the absolute temperature. 

The specific heat of air is the number of Btu required to raise the tem- 
perature of 1 Ib of air 1 F. Distinction should always be made between 
the instantaneous specific heat at any existent temperature and the mean 
specific heat, which is the average specific heat through a given tempera- 
ture range. The mean specific heat is the value required in most calcu- 
lations. The specific heats at constant pressure, C p , and the specific 
heats, C v , at constant volume are different. The specific heat at constant 
pressure is commonly used and it varies, under a pressure of one atmos- 
phere, from a minimum at 32 F from which it increases with either increase 
or decrease of temperature. The value of 0.24, as the mean specific heat 
at constant pressure, is sufficiently accurate for use at ordinary tem- 
peratures. Values for instantaneous and mean specific heats are given 
in Table 3. 

The mean specific heat of 'water vapor at cqnstant pressure is taken as 
0.45 for all general engineering computations. 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 1. PROPERTIES OF DRY AiR a 

Barometric Pressure 29.921 In. of Hg 



TaMWRATTRE WEIGHT POUNDS 
DIG F PBB Cc FT 


i 

RATIO OF 
VOLUME TO 
VOLTME AT 70 F 


BTTJ ABSORBED BY 
ONE CTT FT DRY 
Am PEE DEQ F 


Cu FT DRY 
AIR WARMED 
ONE DEG 
PER BTTJ 





0.08633 


0.8678 


0.02077 


48.15 


10 


0.08449 


0.8867 


0.02030 


49.26 


20 


0.08273 


0.9056 


0.01986 


50.35 


30 0.08104 


0.9245 


0.01944 


51.44 


40 


0.07942 


0.9433 


0.01905 


52.49 


50 


0.07785 


0.9624 


0.01868 


53.36 


60 


0.07636 


0.9811 


0.01832 


54.44 


70 


0.07492 


1.0000 


0.01798 


55.62 


80 


0,07353 


1.0189 


0.01765 


56.66 


90 


0.07219 


1.0378 


0.01733 


57.70 


100 


0.07090 


1.0567 


0.01702 


58.75 


110 


0.06966 


1.0755 


0.01672 


59.81 


120 


0.06845 


1.0946 


0.01643 


60.86 


130 


0.06729 


1.1133 


0.01616 


61.88 


140 


0.06617 


1.1322 


0.01589 


62.93 


150 


0.06509 


1.1510 


0.01563 


63.98 


160 


0.06403 


1.1701 


0.01538 


65.02 


180 


0.06203 


1.2078 


0.01490 


67.11 


200 


0.06015 


1.2456 


0.01446 


69.24 


220 


0.05838 


1.2832 


0.01403 


71.27 


240 


0.05671 


1.3211 


0.01364 


73.31 


260 


0.05514 


1.3587 


0.01326 


75.41 


280 


0.05365 


1.3965 


0.01291 


77.46 


300 


0.05223 


1.4344 


0.01257 


79.55 


350 


0.04901 


1.5287 


0.01181 


84.67 


400 


0.04615 


1.6234 


0.01114 


89.67 


450 


0.04362 


1.7176 


0.01054 


94.87 


500 


0.04135 


1.8119 


0.01001 


99.01 


550 


0.03930 


1.9064 


0.00953 


104.93 


600 


0.03744 


2.0011 


0.00908 


110.13 


700 


0.03422 


2.1893 


0.00833 


120.05 


800 


0.03150 


2.3784 


0.00769 


130.04 


900 


0.02911 


2.5737 


0.00713 


140.25 


1000 


0.02718 


2.7564 


0.00668 


149.70 



H> Sev 5 M - b 3 8ed on the instantaneous specific heats of air. 



CHAPTER 1. AIR, WATER AND STEAM 



TABLE 2. PROPERTIES OF SATURATED AiR a 

Weights of Air, Vapor and Saturated Mixture of Air and Vapor at 29.921 In. of Hg 



TEMP. 
DsoF 


WEIGHT IN A CUBIC FOOT OP MEKTUBE 


BTU 
ABSORBED 
BY ONE 
CUBIC 
FOOT 
SAT. Am 
PER DEO F 


CUBIC 
FEET 
SAT. Am 
WARMED 
ONE DEO 
PEE BTU 


SPECIFIC 
HEAT BTU 
PER POUND 

OP 

MIXTURE 


Weight of 
Dry Air 
Pounds 


Weight of 
Vapor 
Pounds 


Total Weight 
ofMirture 
Pounds 





0.08622 


0.000068 


0.08629 


0.02078 


48.12 


0.2408 


10 


0.08431 


0.000111 


0.08442 


0.02031 


49.24 


0.2406 


20 


0.08244 


0.000177 


0.08262 


0.01987 


50.33 


0.2405 


30 


0.08060 


0.000278 


0.08088 


0.01946 


51.39 


0.2406 


40 


0.07876 


0.000409 


0.07917 


0.01908 


52.41 


0.2410 


50 


0.07692 


0.000587 


0.07751 


0.01872 


53.42 


0.2415 


60 


0.07503 


0.000828 


0.07586 


0.01838 


54.41 


0.2423 


70 


0.07307 


0.001151 


0.07422 


0.01805 


55.40 


0.2432 


80 


0.07099 


0.001578 


0.07257 


0.01775 


56.34 


0.2446 


90 


0.06877 


0.002134 


0.07090 


0.01747 


57.24 


0.2464 


100 


0.06634 


0.002851 


0.06919 


0.01721 


58.11 


0.2487 


110 


0.06361 


0.003762 


0.06737 


0.01696 


58.96 


0.2517 


120 


0,06057 


0.004912 


0.06548 


0.01675 


59.70 


0.2558 


130 


0.05712 


0.006344 


0.06346 


0.01657 


60.35 


0.2611 


140 


0.05317 


0.008116 


0.06129 


0.01642 


60.91 


0.2679 


150 


0.04863 


0.010284 


0.05891 


0.01630 


61.35 


0.2767 


160 


0.04339 


0.012919 


0.05631 


0.01624 


61.58 


0.2884 


170 


0.03733 


0.016092 


0.05342 


0.01621 


61.69 


0.3034 


180 


0.03033 


0.019888 


0.05022 


0.01624 


61.58 


0.3234 


190 


0.02228 


0.024384 


0.04666 


0.01633 


61.24 


0.3500 


200 


0.01298 


0.029700 


0.04268 


0.01649 


60.64 


0.3864 


210 


0.00230 


0.035932 


0.03616 


0.01672 


59.81 


0.4624 


212 


0.00000 


0.037286 


0.03729 


0.01818 


55.01 


0.4875 



^Compiled by W. H. Severns, based on the instantaneous specific heats of air. 

TABLE 3. SPECIFIC HEATS OF DRY AiR a 

Constant Barometric Pressure of 29.921 In. of Hg 



TEMPERATURE 
DE0F 


INSTANTANEOUS 

OSTBUB 

SPECIFIC HEAT 


TEMPERATUBE 
RANGE 
DBGF 


MEAN 
SPECIFIC 
HEAT 


-301.0 


0.2520 


32 to 212 


0.2401 


-108.4 


0.2430 


32 to 392 


0.2411 


32.0 


0.2399 


32 to 752 


0.2420 


212.0 


0.2403 


32 to 1112 


0.2430 


392.0 


0.2413 







752.0 


0.2430 








1112.0 


0.2470 









Compiled by W. H. Severna, based on data given in the International Critical Tables. 

5 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



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CHAPTER 1. AIR, WATER AND STEAM 



Table 4 is intended to aid in determining the density of moist air, 
taking into account its temperature, pressure, and moisture content. 

Example 1. To show the use of Table 4: Given air at 83 F dry-bulb and 68 F wet- 
bulb (or a depression of 15 deg) with a barometric pressure of 29.40 in. of mercury. 
What will be the weight of this air in pounds per cubic foot? 

Solution. From Table 4 the weight of saturated air at 80 F and 29.00 in. barometer is 
found to be 0.07034 Ib per cubic foot. There is a decrease of 0.00015 Ib per degree dry- 
bulb temperature above 80 F. There is an increase of 0.00025 Ib for each 0.1 in. above 
29.00 in. From the last column of Table 4 it is found that there is an increase of approxi- 
mately 0.000035 Ib per degree wet-bulb depression when the dry-bulb is 83 F. Tabu- 
lating the items: 

0.07034 = weight of saturated air at 80 F and 29.00 bar. 

- 0.00045 decrement for 3 deg dry-bulb, 3 X 0.00015. 

+ 0.00100 = increment for 0.4 in. bar., 4 X 0.00025. 

+ 0.00053 = increment for 15 deg wet-bulb depression, 15 X 0.000035. 

0.07142 = weight in pounds per cubic foot of air at 83 F dry-bulb, 68 F wet-bulb, 
29.40 in. bar. 

It is usual to assume that dry air, moist air, and the water vapor in the 
air follow the laws of perfect gases. This assumption while not absolutely 
true, especially with saturated vapor at temperatures much above 140 F, 
is sufficiently accurate for practical purposes and it greatly simplifies 
computations. 

Boyle's Law refers to the relation between the pressure and volume of a 
gas, and may be stated as follows : With temperature constant, the volume of 
a given weight of gas varies inversely as its absolute pressure. Hence, if 
PI and P 2 represent the initial and final absolute pressures, and V\ and 
F 2 represent corresponding volumes of the same mass, say one pound of 

FT -p 

gas, then^~ = -= 2 , or Pi Vi = P 2 F 2 , but since Pi 7i for any given case is 

V 2 Jri 

a definite constant quantity, it follows that the product of the absolute 
pressure and volume of a gas is a constant, or PV = C, when T is kept 
constant. Any change in the pressure and volume of a gas at constant 
temperature is called an isothermal change. 

Charles 1 Law refers to the relation among pressure, volume, and tem- 
perature of a gas and may be stated as follows : The volume of a given 
weight of gas varies directly as the absolute temperature at constant pressure, 
and the pressure varies directly as the absolute temperature at constant 

volume. Hence, when heat is added at constant volume, F c , the resulting 
p *p 

equation is ^ = -=r, or, for the same temperature range at constant pres- 
"\ -LI 

V z T* 

sure, PC, the relation is = TF- 
1/1/1 

In general, for any weight of gas, T7, since volume is proportional to 
weight, the relation among P, F, and T is 

PV = WRT (3) 

where 

P = the absolute pressure of the gas, pounds per square foot. 
V = the volume of the weight W, cubic feet. 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

W = the weight of the gas, pounds. 

R * a constant depending on the nature of the gas. The average value of R for air 

is 53.34. 
T the absolute temperature, degrees Fahrenheit. 

This is the characteristic equation for a perfect gas, and while no gases 
are perfect in this sense, they conform so nearly that Equation 3 will 
apply to most engineering computations. 

HUMIDITY 

Humidity is the water vapor mixed with dry air in the atmosphere. 
Absolute humidity has a multiplicity of meanings, but usually the term 
refers to the weight of water vapor per unit volume of space occupied, 
expressed in grains or pounds per cubic foot. With this meaning, absolute 
humidity is nothing but the actual density of the water vapor in the 
mixture and might better be so called. A study of Keenan's Steam 
Tables 2 indicates that water vapor, either saturated or super-heated,^ at 
partial pressures lower than 4 in. of mercury may be treated as a gas with 
a gas constant R of 1.21 in the characteristic equation of the gas pV 
wR (t + 460). Within such limits, the density (d) of water vapor is 



1.2! (-f 460) 
5785 e 



(P ounds *** cubic foot ) 



460 



(grains per cubic foot) (4b) 



where 

e actual partial pressure of vapor, inches of mercury. 
t dry-bulb temperature, degrees Fahrenheit. 

Specific Humidity 

It simplifies many problems which deal with mixtures of dry air and 
water vapor to express the weight or the mass of the vapor in terms of the 
weight or the mass of dry air. If the weight of the water vapor in a 
mixture be divided by the weight of the dry air, and the weight of dry air 
be made unity, we have an expression of the weight of water vapor carried 
by a unit weight of dry air. This relation has no generally accepted name. 
It has been variously called: mixing ratio, proportionate humidity, mass 
or density ratio, absolute humidity, and specific humidity. Of all these 
terms specific humidity is the most suggestive of the meaning which it is 
desired to express and it has found considerable use in this sense even 
though it is defined in International Critical Tables as the ratio of the 
mass of vapor to the total mass. It will be understood here that specific 
humidity refers to the weight of water vapor carried by one pound of 
dry air. 

The gas constant for dry air, when the partial pressure of the air is 
expressed in inches of Hg, is 0.753; so that the specific humidity, if 
represented by W, is 



"Published by American Society of Mechanical Engineers, see abstract in Table 8. 

8 



CHAPTER 1. AIR, WATER AND STEAM 



W - 



B-e 



1.21 (t + 460) 
= 0.622 - 



0.753 (t + 460) 
(pounds) 



(5a) 
(5b) 



-4354 () (grains) 

where 

e = actual partial pressure of vapor, inches of mercury. 
B = total pressure of mixture (barometric pressure), inches of mercury. 

Relative Humidity 

Relative humidity ($) is either the ratio of the actual partial pressure, 
e, of the water vapor in the air to the saturation pressure, e t , at the dry- 
bulb temperature, or the ratio of the actual density, d, of the vapor to 
the density of saturated vapor, dt, at the dry-bulb temperature. That is: 

The relative humidity of a given mixture at a.giyen temperature is not 
the same as the specific humidity, W, of the mixture divided by the 
specific humidity, W t , of saturated vapor at the same temperature, for 
from Equations 5a and 6 



Wt - - 622 



0.622 



(-=*-) 

\ B-et ) 



B 



(7) 



The specific humidity of an unsaturated air-vapor mixture cannot, 
therefore, be accurately found by multiplying the specific humidity of 
saturated vapor by its relative humidity; although the error is usually 
small especially when the relative humidity is high. 

With a relative humidity of 100 per cent, the dry-bulb, wet-bulb, and 
dew-point temperatures are equal. With a relative humidity less than 
100 per cent, the dry-bulb exceeds the wet-bulb, and the wet-bulb exceeds 
the dew-point temperature. 

RELATION OF DEW POINT TO RELATIVE HUMIDITY 

A peculiar relationship exists between the dew-point and the relative 
humidity and this is found most useful in air conditioning work. This 
relationship is, that for a fixed relative humidity there is substantially a 
constant difference between the dew-point and the dry-bulb temperature 
over a considerable temperature range. Table 5, giving the dry-bulb and 
dew-point temperatures and the dew-point differentials for 50 per cent 
relative humidity, illustrates this relationship clearly. 

TABLE 5. TEMPERATURES FOR 50 PER CENT RELATIVE HUMIDITY 



Dry-bulb temperature..... .. 


65.0 


70.0 


75.0 


80.0 


85.0 


90.0 


Dew-point temperature. 


45.8 


50.5 


55.25 


59.75 


64.25 


68.75 


Difference between dew-point and dry- 
bulb temperature 


19.2 


19.5 


19.75 


20.25 


20.75 


21.25 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

It will be seen from an inspection of this table that the difference 
between the dew-point temperature and the room temperature is approxi- 
mately 20 deg throughout this range of dry-bulb temperatures or, to 
be more exact, the differential increases only 10 per cent for a range of 
practically 25 deg. 

This principle holds true for other humidities and is due to the fact 
that the pressure of the water vapor practically doubles for every 20 deg 
through this range. 

The approximate relative humidity for any difference between dew- 
point and dry-bulb temperature may be expressed in per cent as: 

100 
2 ^ W 

where 

/ I = dew-point temperature. 

This principle is very useful in determining the available cooling effect 
obtainable with saturated air when a desired relative humidity is to be 
maintained in a room, even though there may be a wide variation in room 
temperature. This problem is one which applies to certain industrial con- 
ditions, such as those in cotton mills and tobacco factories, where re- 
latively high humidities are carried and where one of the principal prob- 
lems is to remove the heat generated by the machinery. It also permits 
the use of a differential thermostat, responsive to both the room tempera- 
ture and the dew-point temperature, to control the relative humidity 
in the room. 

Table 6 gives, for different temperatures, the density of saturated vaporr 
d t , the weight of saturated vapor mixed with 1 lb of dry air, W t , (at a 
relative humidity of 100 per cent and a barometric pressure, B, of 29.92 in. 
of^mercury), the specific volume of dry air, and the volume of an air-vapor 
mixture containing 1 Ib of dry air (at a relative humidity of 100 per cent 
and a pressure of 29.92 in. of mercury). The preceding equations or the 
data from Table 6 may be conveniently used in solving the following- 
typical problems: 5 




*& to be maintained at 70 F with a relative 
= 04) when the outside air is at F and 70 per cent 
a baro < netric P ress ^' *> of 29.92 in. of mercury Fmd 
t0 *"* V** f dry air and *** dew 'P int temperature 

Solution. From Equation 5a and Table 6, 

W l = 0.622 (29.92-0.0264) " - 000548 lb Pr Pound of dry air. 

W, - 0.622 ( 29.92 X - olfg ) = ' 00618 lb *>* Pund of dry air. 



An approximation of the same result from Table 6 is 

Wk - 0.4 X 0.01574 = 0.006296 lb per pound o?dry a i? 

10 



CHAPTER 1. AIR, WATER AND STEAM 



The water vapor added per pound of dry air is approximately 0.00574636 Ib and the 
dew-point temperature is approximately 45 F. The degree of approximation is evident. 

Example 8. Dehumidifying and Cooling. Air with a dry-bulb temperature of 84 F, 
a wet-bulb of 70 F, or a relative humidity of 50 per cent ($ = 0.5), and a barometric 
pressure, B, of 29.92 in. of mercury is to be cooled to 54 F, Find the dew-point tem- 
perature of the entering air and the weight of vapor condensed per pound of dry air. 

Solution. From Equation 5a and Table 6, 

w l - 0.622 - " ' 01248 lb per pound of dry air * 



' 622 " " - 00887 Ib Per P Und 



Since W\ Wt when t 63.4 F, this is the dew-point temperature of the entering air. 
The weight of vapor condensed is (Wi W^ or 0.00361 lb per pound of dry air. 

An approximate result is 

Wi - 0.5 X 0.02543 - 0.012715 lb per pound of dry air. 

Wt = 1 X 0.008856 = 0.008856 lb per pound of dry air, since the exit air is saturated. 

Since W\ Wt at t 64 F, this is the dew-point temperature of the entering air. 
The weight of vapor condensed is 0.003859 lb per pound of dry air. The degree of approxi- 
mation is again evident. 

ADIABATIC SATURATION OF AIR 

The process of adiabatic saturation of air is of considerable importance 
in air conditioning. Suppose that 1 lb of dry air, initially unsaturated but 
carrying W lb of water vapor with a dry-bulb temperature, /, and a wet- 
bulb temperature, f, be made to pass through a tunnel containing an 
exposed water surface. Further assume the tunnel to be completely in- 
sulated, thermally, so that the only heat transfer possible is that between 
the air and water. As the air passes over the water surface, it will gradu- 
ally pick up water vapor and will approach saturation at the initial wet- 
bulb temperature of the air, if the water be supplied at this wet-bulb tem- 
perature. During the process of adiabatic saturation, then, the dry-bulb 
temperature of the air drops to the wet-bulb temperature as a limit, the 
wet-bulb temperature remains substantially constant, and the weight of 
water vapor associated with each pound of dry air increases to Wv, as a 
limit, where Wv is the weight of saturated vapor per pound of dry air for 
saturation at the wet-bulb temperature. 

Example 4- If air with a dry-bulb of 85 F and a wet-bulb of 70 F be saturated adia- 
batically by spraying with recirculated water, what will be the final temperature and the 
vapor content of the ah-? 

Solution. The final temperature will be equal to the initial wet-bulb temperature or 
70 F, and since the air is saturated at this temperature, from Table 6, W - 0.01574 lb 
per pound of dry air. 

In the adiabatic saturation process, since the heat given up by the dry 
air and associated vapor in cooling to the wet-bulb temperature is utilized 
in evaporation of water at the wet-bulb temperature, W H. Carrier has 
pointed out 8 that the equation for the process of adiabatic saturation, and 
hence for a process of constant wet-bulb temperature, is: 



'Rational Psychrometric Formulae, by W. H. Carrier (A.S.M.E. Transactions, Vol. 33, 1911, p 1005.) 

11 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



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HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Via (W v - W) = c^ (t - *') + c s W (t - *') (9a) 

and using c Pa 0.24 and c^ = 0.45 

fc f f 8 (Wti - WO - (0.24 + 0.45J7) (/ - *) (9b) 

where 

A ! fg latent heat of vaporization at t\ Btu per pound. 

(Wt* f W} = increase in vapor associated with 1 Ib of dry air when it is saturated 
adiabatically from an initial dry-bulb temperature, t t and an initial vapor content, W. 
pounds. 

Knowing any two of the three primary variables, t, t', or W, the third 
may be found from this equation for any process of adiabatic saturation. 

TOTAL HEAT AND HEAT CONTENT 

The total heat of a mixture of dry air and water vapor was originally 
defined by W. H. Carrier as 

S - c^(t - 0) + W [A'f g + c^(t - /')] (10) 

where 

S = total heat of the mixture, Btu per pound of dry air. 
pa raean specific heat at constant pressure of dry air. 
Cpg mean specific heat at constant pressure of water vapor. 
/ = dry-bulb temperature, degrees Fahrenheit. 
t 1 = wet-bulb temperature, degrees Fahrenheit. 

W = weight of water vapor mixed with each pound of dry air, pounds. 
#f g = latent heat of vaporization at t 1 , Btu per pound. 

Since this definition holds for any mixture of dry air and water vapor, 
the total heat of a mixture with a relative humidity of 100 per cent and at 
a temperature equal to the wet-bulb temperature (/') is 



By equating Equation lOto Equation 11, the equation for the adiabatic 
saturation process, Equation 9a, follows. This demonstrates that the 
adiabatic saturation process at constant wet-bulb temperature is also a 
process of constant total heat. In short, the total heat of a mixture of dry 
air and water vapor is the same for any two states of the mixture at the 
same wet-bulb temperature. This fact furnishes a convenient means of 
finding the total heat of an air-vapor mixture in any state. 

Enthalpr 

T, J? iS to . tal . heat of J^ air-vapor mixture is not exactly equal to the true 
heat content;or enthalpy of the mixture since the heat content of the 
liquid is not included in Equation 10. With the meaning of hea? content 
m agreement with present practise in other branches of liermodynamics 
the true heat content of a mixture of dry air and water vapor (SthTp 

?o S r ?he S&ol^ and the "^^ *** at 32 F tie datum 



22 



CHAPTER 1, AIR, WATER AND STEAM 



h c Pa (t - 0) -f W h 9 = 0.24 (* - 0) + W k s (12) 

where 

h the heat content of the mixture, Btu per pound of dry air. 
t = the dry-bulb temperature, degrees Fahrenheit. 
W = the weight of vapor per pound of dry air, pounds. 
h s = the heat content of the vapor in the mixture, Btu per pound. 

The heat content of the water vapor in the mixture may be found in 
steam charts or tables when the dry-bulb temperature and the partial 
pressure of the vapor are known. Or, since the heat content of steam at 
low partial pressures, whether super-heated or saturated, depends only 
upon temperature, the following empirical equation, derived from Proper- 
ties of Saturated Steam by J. H. Keenan, Table 8, may be used: 

h s - 1059.2 + 0.45 /' (13) 

Substituting this value of h& in Equation 12, the heat content of the 
mixture is 

h = 0.24 (t - 0) + W (1059.2 + 0.45 * ! ) (14) 

Example 5. Find the total heat of an air-vapor mixture having a dry-bulb tem- 
perature of 85 F and a wet-bulb temperature of 70 F. 

Solution. From Table 6, for saturation at the wet-bulb temperature, W = 0.01574, 
and from Equation 14, 

h = 0.24 (70-0) + 0.01574 [1059.2 + (0.45 X 70)] = 33.96 Btu per pound dry air. 

By considering the temperatures in Table 6 to be wet-bulb readings, the 
enthalpy of any air-vapor mixture may be obtained from the last column 
in the table. 

An energy equation can be written that applies, in general, to various 
air conditioning processes, and this equation can be used to determine the 
quantity of heat transferred during such processes. In the most general 
form, this equation may be explained with the aid of Fig. 1 as follows. 

The rectangle may represent any apparatus, e.g., a drier, humidifier, dehumidifier, 
cooling tower, or the like, by proper choice of the direction of the arrows. 

In general, a mixture of air and water vapor, such as atmospheric air, enters the 
apparatus at 1 and leaves at 3. Water is supplied at some temperature, &. For the flow 
of 1 Ib of dry air (with accompanying vapor) through the apparatus, provided there is no 
appreciable change in the elevation or velocity of the fluids and no mechanical energy 
delivered to or by the apparatus, 

h + h + (W, - W,) A, = h, + Re 

or 

E h - RC - h, - A, - (W, - W,) A,' (15) 

where 

E h = the quantity of heat supplied per pound of dry air, Btu. 

RC the quantity of heat lost externally by heat transfer from the apparatus. 

Btu per pound of dry air. 

Wi = the weight of water vapor entering, per pound of dry air. 
Wz the weight of water vapor leaving, per pound of dry air. 
}i* = the heat content of the water supplied at h, Btu per pound. 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Aa hi = the increase in the heat content of the air-water vapor mixture in passing 
through the apparatus, Btu per pound of dry air 

- 0.24 (/, - ft) + Wi (1059.2 + 0.45 /) - Wi (1059.2 + 0.45fc) 

The net quantity of heat added to or removed from air-water vapor 
mixtures in air conditioning work is frequently approximated by taking 
the differences in total heat at exit and entrance. 

For example, in Fig. 1, an approximate result is 

h - -Re = Sa - Si (16) 

where 

Sj the total heat of the air- vapor mixture at exit, Btu per pound of dry air. 

Si the total heat of the air-vapor mixture at entrance, Btu per pound of dry air. 



W i Ib, Water Vapor 
lib. Dry Air 




W 3 Ib. Water Vapor 
lib. Dry Air 



r?r 

<W 5 -H$)lb. Water 

FIG. 1. DIAGRAM ILLUSTRATING ENERGY EQUATION 15 

From the definitions of total heat and heat content, it may be demon- 
strated that Equation 16 is exactly equivalent to Equation 15, when, and 
only when, t\ = t\ = fa; i.e., when the initial and final wet-bulb tempera- 
tures and the temperature of the water supplied are equal. The one pro- 
cess that meets these conditions is adiabatic saturation, and either 
equation will give a^result of zero; for other conditions, Equation 16 is 
approximate but satisfactory for many calculations. 

The following problems illustrate the application of these principles: 

&cample 6. Heating (data from Example 2). Assuming the water to be supplied at 
60 F, the net quantity of heat supplied is, from Equation 15, 

h - Re - 0.24 (70 - 0) + 0.000548 X 0.45 (70 - 0) + 0.005632 
[1059.2 + 0.45 X 70 - (50 - 32)] - 22.90 Btu per pound of dry air. 

Cooling (data from Example 3). If the condensate is removed at 54 F 
* removed is found from Equation 15, by proper regard to the arrow 



fa + #c - 0.24 (84 - 54) + 0.00887 X 0.45 (84 - 54) + 00361 
[1059.2 + 0.45 X 84 - (54 - 32)] - 11. 24 Btu per pound of dry air. 

*-> the wet-bulb 

fr - m ^K 6 ' since ** t air is saturated, 22.55 Btu per 
quantity of heat removed is, approximately 

f dry air< The degree f appr - mat - ^ 



24 



CHAPTER 1. AIR, WATER AND STEAM 



PSYCHROMETRIC CHART 

The revised Bulkeley Psychrometric Chart 4 , will be found attached to 
the inside back cover. It shows graphically the relationships expressed 
in Equations 9a and 9b. It also gives the grains of moisture per pound of 
dry air for saturation, the grains of moisture per cubic foot of saturated 
air, the total heat in Btu per pound of dry air saturated with moisture, 
and the weight of the dry air in pounds per cubic foot. Fig. 2 shows the 
procedure to follow in using the Bulkeley Chart. The directrix curves 
above the saturation line are as follows: 

A is the total heat in Btu contained in the mixture above F, and is to be referred 
to the column of figures at the left side of the chart. Heat of the liquid is not included. 




A, B, C, D, E, FaDirectrix lines 
D. B. LDry bulb line 
D. P. L=Dew point line 



R. H. L=Relative humidity line 
W.B.1_= Wet bulb line 
Sl= Saturation line 



G. P. Lb Grains moisture sat mixture per Ib dry air R. D. D. S.= Relative density dry air per cu ft saturated 

T. H.=Total heat sat mixture per Ib dry air W. P. C. F. S.= Weight per cu ft in Ibs saturated 

V. P.Vapor pressure in mm mercury R. D. S.*Relative density per cu ft saturated 

G. P. C. F. S.=Grains moisture per cu ft sat air W. P. C. F. D. Weight per cu ft in Ibs dry 

W. D. A. C. F. S.=Weight dry air per cu ft in Ibs saturated R. D. D.=Relative density per cu ft dry 



W. P. C. F. x 
R. D.x 



- w - p - c - F - * parta ' MturaBon 



FIG. 2 DIAGRAMS SHOWING PROCEDURE TO FOLLOW IN USING BULKELEY CHART 

B is the grains of moisture of water vapor contained in each pound of the saturated 
mixture and is to be referred to the figures at the left side of the chart. 

C is the grains of moisture of water vapor per cubic foot of saturated mixture, and is 
to be referred to the figures at the left side of the chart which are to be divided by 10. 

D is the weight in decimal fractions of a pound of dry air in one cubic foot of the 
saturated mixture, and is referred to the first column of figures to the right of the satura- 
tion line between the vertical dry-bulb temperature lines 170 and 180 F. The relative 
density of the mixture is read in a similar manner from the same curve by the column of 
figures between the vertical dry-bulb temperature lines 180 and 190 F. 

E is similar to D but is for one cubic foot of the saturated mixture. 



The Bulkeley Psychrometric Chart was presented to the Society in 1926. (See A.S.H.V.E. TRANS- 
ACTIONS, Vol. 32, 1926, p. 163.) Single copy of the chart can be furnished at a cost of $ .25. 



HEATING VENTIUITING AIR CONDITIONING GUIDE 1938 

F is similar to D but is for dry air, devoid of all moisture or water vapor. For con- 
venience, the approximate absolute temperature of 500 F is given at 40 F on the satura- 
tion line for the purpose of calculating volume, weight per cubic foot, and relative density 
at partial saturation. 



METHOD OF USING THE CHART 

Relati 

__., line, t 

as 46 per cent. 



Example 8. Relative Humidity: At the intersection of the 78 F wet-bulb line and the 
95 F dry-bulb line, the relative humidity is read directly on the straight diagonal lines 
as 46 per cent. 

Example 9. Dew Point: At the intersection of the 78 F wet-bulb line, the dew-point 
temperature is read directly on the horizontal temperature lines as 70.9 F. 

Example 10. Vapor Pressure: At the intersection of the 78 F wet-bulb line and the 
95 F ^dry-bulb line, pass in a horizontal direction to the left of the chart and on the 
logarithmic scale read the vapor pressure as 19.4 millimeters of mercury. (Divide by 
25.4 for inches.) 

Example 11. Total Heat Above F in Mixture per Pound of Dry Air Saturated with 
Moisture: From where the wet-bulb line joins the saturation line, pass in a vertical 
direction on the 78 F dry-bulb line to its intersection with curve A and on the logarithmic 
scale aMhe left of the chart read 40.6 Btu per pound of mixture. The use of this curve 
to obtain the total heat in the mixture at any wet-bulb temperature is a great con- 
venience, as the number of Btu required to heat the mixture and humidify it, as well as 
the refrigeration required to cool and dehumidify the mixture, can be obtained by 
taking the difference in total heat before and after treatment of the mixture. 

Example 12. Grains of Moisture per Pound of Dry Air Saturated with Moisture: 
From 70.9 F dew-point temperature on the saturation line, pass vertically to the inter- 
section with curve B and on the logarithmic scale at the left read 114 grains of moisture 
per pound. 

Example 1$.^ Grains of Moisture per Cubic Foot of Mixture, Partially Saturated: From 
/0.9 F dew-point temperature on the saturation line proceed in a vertical direction to 
curve C, and on the logarithmic scale to the left read 83.3 which, divided by 10 gives 
S.d3 grains. A temperature of 70.9 F is equal to an absolute temperature of 530.9, and 
95 F equals 555, absolute temperature. Therefore, ^ x 8>33 . 7 97 gr ^ n& pcf 
cubic foot of partially saturated mixture. 

Example 14. Grains of Moisture per Cubic Foot of Saturated Air: Starting at the 
saturation line at the desired temperature, pass in a vertical direction to curve C and on 
the logarithmic scale at the left, read a number which, divided by 10, will give the 
answer. 

Example IS. Weight per Cubic Foot of Dry A ir and Relative Density: From the point 

^rr3mTK e 'v he 1? F < vertical dry ' bulb Iine intersects cu ro - Pass to right P We 
and read 0.075 Ib; if cubic feet per pound are desired, divide 1 by this amount The 
relative density is read immediately to the right as 1.00. <" UU ni. me 



i" per C^Foot f Saturated Mixture and Relative 
V n t r,v '- f r exaffl P'e, the 70 F vertical line intersects the curve 

4,7"* per cublc foot as - 07316 



Partially 

si 



Therefore, ^ = 0.851. The weight of 1 cu ft of air at 50 F dry-bulb and 46 F wet-bulb 

x ' 851 = a 6675 - and the relative dens * v 1-046 



26 



CHAPTER 1. AIR, WATER AND STEAM 



PROPERTIES OF WATER 

Composition of Water. Water is a chemical compound (H 2 O) formed by 
the union of two volumes of hydrogen and one volume of oxygen, or two 
parts by weight of hydrogen and 16 parts by weight of oxygen. 

Density of Water. Water has its greatest density at '39.2 F, and it 
expands when heated or cooled from this temperature. At 62 F a U. S. 
gallon of 231 cu in. of water weighs approximately 8% Ib, and a cubic foot 
of water is equal to 7.48 gal. The specific volume of water depends on the 
temperature and it is always the reciprocal of its density. (See Table 7.) 

TABLE 7. THERMAL PROPERTIES OF WATER 



TEMPERATURE 
DEGF 


SAT. PRESS. 
LB PER SQ IN. 


VOLUME Cu FT 
raaLs 


WEIGHT LB PER 
CuFi 


SPECIFIC 
HEAT 


32 


0.0887 


0.01602 


62.42 


1.0093 


40 


0.1217 


0.01602 


62.42 


1.0048 


50 


0.1780 


0.01602 


62.42 


1.0015 


60 


0.2561 


0.01603 


62.38 


0.9995 


70 


0.3628 


0.01605 


62.31 


0.9982 


80 


0.5067 


0.01607 


62.23 


0.9975 


90 


0.6980 


0.01610 


62.11 


0.9971 


100 


0.9487 


0.01613 


62.00 


0.9970 


110 


1.274 


0.01616 


61.88 


0.9971 


120 


1.692 


0.01620 


61.73 


0.9974 


130 


2.221 


0.01625 


61.54 


0.9978 


140 


2.887 


0.01629 


61.39 


0.9984 


150 


3.716 


0.01634 


61.20 


0.9990 


160 


4.739 


0.01639 


61.01 


0.9998 


170 


5.990 


0.01645 


60.79 


1.0007 


180 


7.510 


0.01650 


60.61 


1.0017 


190 


9.336 


0.01656 


60.39 


1.0028 


200 


11.525 


0.01663 


60.13 


1.0039 


210 


14.123 


0.01669 


59.92 


1.0052 


212 


14.696 


0.01670 


59.88 


1.0055 


220 


17.188 


0.01676 


59.66 


1.0068 


240 


24.97 


0.01690 


59.17 


1.0104 


260 


35.43 


0.01706 


58.62 


1.0148 


280 


49.20 


0.01723 


58.04 


1.0200 


300 


67.01 


0.01742 


57.41 


1.0260 


350 


134.62 


0.01797 


55.65 


1.0440 


400 


247.25 


0.01865 


53.62 


1.0670 


450 


422.61 


. 0.01950 


51.30 


1.0950 


500 


681.09 


0.02050 


48.80 


1.1300 


550 


1045.4 


0.02190 


45.70 


1.2000 


600 


1544.6 


0.02410 


41.50 


1.3620 


700 


3096.4 


0.03940 


25.40 






Water Pressures. Pressures are often stated in feet or inches of water 
column. At 62 F, with h equal to the head in feet, the pressure of a 
column of water is 62.383fe Ib per square foot, or 0.433fe Ib per square inch. 
A column of water 2.309 ft (27.71 in.) -high exerts a pressure of one pound 
per square inch at 62 F. 

Boiling Point of Water. The boiling point of water varies with the 
pressure; it is lower at higher altitudes. A change in pressure will always 
be accompanied by a change in the boiling point, and there will be a cor- 

27 



HEATING 


VENTILATING AIR CONDITIONING GUIDE 1938 


TABLE 8. PROPERTIES OF 

Specific Volume 
/*!?&. SS'F. lid Erap. V?^r 

p t Vf Vfc v g 

WH* 58.83 0.01603 1256.9 1256.9 


SATURATED STEAM: 

Total Heat 
Sat. Sat. 
Liquid Evap. Vapor 

hf hfg tr 
26.88- 1058.8 1085.7 


PRESSURE TABLE* 

Entropy 

Liquid Evap. Vapor Lb./Sq. JS 
8f * Sfg Sg p 
0.0533 2.0422 2.0955 WH* 


%"H& 70.44 


0.01605 


856.5 


856.5 


38.47 


10523 


1091.0 


0.0754 


1.9856 2.0609 


%"Hff 


l"Hj 


r 79.06 


0.01607 


652.7 


652.7 


47.06 


1047.8 


1094.9 


0.0914 


1.9451 


2.0365 


l"H ff 


V&" Hi 


r 91.75 


0.01610 


4453 


4453 


59.72 


1040.8 


1100.6 


0.1147 


1.8877 


2.0024 


WHff 


2"H* 101.17 


0.01613 


339.5 


3393 


69.10 


1035.7 


1104.8 


0.1316 


1.8468 


1.9784 


2" Hi 


2'4"Hfi 


r 108.73 


0.01616 


2752 


2752 


76.63 


10313 


1108.1 


0.1450 


1.8148 


1.9598 


2i/ 2 ;;H ff 


3"Hgr 115.08 


0.01618 


231.8 


231.8 


82.96 


1027.9 


1110.8 


0.1561 


1.7885 


1.9446 




1.0 


101.76 


0.01614 


333.8 


333.9 


69.69 


10353 


1105.0 


0.1326 


1.8442 1.9769 


1.0 


2.0 


126,10 


0.01623 


173.94 


173.96 


93.97 


1021.6 


1115.6 


0.1750 


1.7442 


1.9192 


2.0 


3.0 


141.49 


0.01630 


118.84 


118.86 


10933 


1012.7 


1122.0 


02009 


1.6847 


1.8856 


3.0 


4.0 


152.99 


0.01636 


90.72 


90.74 


120.83 


1005.9 


1126.8 


02198 


1.6420 


1.8618 


4.0 


5.0 


16225 


0.01641 


7339 


73.61 


130.10 


1000.4 


1130.6 


02348 


1.6088 


1.8435 


5.0 


6.0 


170.07 


0.01645 


62.03 


62.05 


137.92 


995.8 


1133.7 


02473 


13814 


1.8287 


6.0 


7.0 


176.85 


0.01649 


53.68 


53.70 


144.71 


991.7 


1136.4 


0.2580 


13582 


1.8162 


7.0 


8.0 


182.87 


0.01652 


4738 


4739 


150.75 


988.1 


1138.9 


02674 


1.5379 


1.8053 


8.0 


9.0 


18828 


0.01*656 


42.42 


42.44 


156.19 


984.8 


1141.0 


02758 


13200 


1.7958 


9.0 


10.0 


19321 


0.01658 


38.44 


3-8.45 


161.13 


981.8 


1143.0 


0.2834 


13040 


1.7874 


10.0 


11.0 


197.75 


0.01661 


35.15 


35.17 


165.68 


979.1 


1144.8 


02903 


1.4894 


1.7797 


11.0 


12.0 


201.96 


0.01664 


32.40 


3Z.42 


169.91 


9763 


1146.4 


02968 


1.4760 


1.7727 


12.0 


13.0 


205.88 


0.01666 


30.06 


30.08 


173.85 


974.1 


1147.9 


03027 


1.4636 


1.7663 


13.0 


14.0 


209.56 


0.01669 


28.05 


28.06 


177.55 


971.8 


11493 


03082 


1.4521 


1.7604 


14.0 


14,696 


212.00 


0.01670 


26.80 


26.82 


180.00 


9702 


1150.2 


03119 


1.4446 


1.7564 


14.696 


16.0 


21632 


0.01673 


24.75 


24.76 


18435 


967.4 


1151.8 


03184 


1.4312 


1.7496 


16.0 


18.0 


222.40 


0.01678 


22.16 


22.18 


190.48 


9633 


1154.0 


03274 


1.4127 


1.7402 


18.0 


20.0 


227.96 


0.01682 


20.078 


20.095 


196.09 


959.9 


1156.0 


03356 


13960 


1.7317 


20.0 


22.0 


233.07 


0.01685 


18363 


18380 


20125 


956.6 


1157.8 


03431 


13809 


1.7240 


22.0 


24.0 


237.82 


0.01689 


16.924 


16.941 


206.05 


953.4 


11593 


03500 


13670 


1.7170 


24.0 


26.0 


242.25 


0.01692 


15.701 


15.718 


210.54 


950.4 


1161.0 


03564 


13542 


1.7106 


26.0 


28.0 


246.41 


0.01695 


14.647 


14.664 


214.75 


947.7 


1162.4 


03624 


13422 


1.7046 


28.0 


30.0 


25034 


0.01698 


13.728 


13.745 


218.73 


945.0 


1163.7 


03680 


13310 


1.6990 


30.0 


32.0 


254.05 


0.01701 


12.923 


12.940 


222.50 


942.5 


1165.0 


03732 


13206 


1.6938 


32.0 


34.0 
36.0 
38.0 


257.58 
260.94 
264.16 


0.01704 
0.01707 
0.01710 


12209 
11.570 
10.998 


12226 
11.587 
11.015 


226.09 
22931 
232.79 


940.0 
937.7 
9353 


1166.1 
11672 
11683 


03783 
03830 
03876 


13107 
13014 
12925 


1.6890 
1.6844 
1.6800 


34.0 
36.0 
38.0 


40.0 
42.0 
44.0 
46.0 
48.0 


26724 
27021 
273.06 
275.81 
278.45 


0.01712 
0.01715 
0.01717 
0.01719 
0.01722 


10.480 
10.010 
9.582 
9.189 
8.829 


10.497 
10.027 
9399 
9207 
8.846 


235.93 
238.95 
241.86 
244.67 
24737 


9333 
9312 
9292 
9272 
925.4 


11692 
11702 
1171.1 
1171.9 
1172.7 


03919 
03961 
0.4000 
0.4039 
0.4076 


12840 
12759 
12682 
12608 
12537 


1.6759 
1.6720 
1.6683 
1.6647 
1.6613 


40.0 
42.0 
44.0 
46.0 
48.0 


60.0 
52.0 
54.0 
66.0 
68.0 


281.01 
283.49 
285.90 
28823 
290.50 


0.01724 
0.01726 
0.01728 
0.01730 
0.01732 


8.496 
8.189 
7.902 
7.636 
7388 


8.514 
8206 
7.919 
7.653 
7.405 


249.98 
25232 
254.99 
25738 
259.71 


923.5 
921.7 
920.0 
9183 
916.6 


11733 
11743 
1175.0 
1175.7 
1176.4 


0.4111 
0.4145 
0.4178 
0.4210 
0.4241 


12469 
12404 
1.2340 
12279 
12220 


1.6580 
1.6549 
1.6518 
1.6489 
1.6461 


50.0 
62.0 
54.0 
56.0 
58.0 


60.0 
62.0 
64.0 
66.0 
68.0 


292.71 
294.85 
296.94 
298.98 
300.98 


0.01735 
0.01737 
0.01739 
0.01741 
0.01743 


7.155 
6.937 
6.732 
6.539 
6357 


7.172 
6.955 
6.749 
6356 
6375 


261.98 
264.18 
26633 
268.43 
270.49 


915.0 
913.4 
911.9 
910.4 
908.9 


1177.0 
1177.6 
11782 
1178.8 
1179.4 


0.4271 
0.4300 
0.4329 
0.4356 
0.4384 


12162 
12107 
12053 
12001 
1.1950 


1.6434 
1.6407 
1.6382 
1.6357 
1.6333 


60.0 
62.0 
64.0 
66.0 
68.0 


70.0 
72.0 
74.0 
76.0 
78.0 


302.92 
304.82 
306.68 
30830 
31028 


0.01744 
0.01746 
0.01748 
0.01750 
0.01752 


6.186 
6.024 
5.870 
5.723 
5384 


6203 
6.041 
5.887 
5.741 
5.602 


272.49 
274.45 
27637 
27825 
280.09 


907.4 
906.0 
904.6 
9032 
901.9 


1179.9 
1180.5 
1181.0 
11813 
1182.0 


0.4410 
0.4435 
0.4460 
0.4485 
0.4509 


1.1900 
1.1852 
1.1805 
1.1759 
1.1714 


1.6310 
1.6287 
1.6265 
1.6244 
1.6223 


70.0 
72.0 
74.0 
76.0 
78.0 


80.0 
82.0 
84.0 
86.0 
88.0 


312.03 
313.74 
315.42 
317.06 
318.68 


0.01754 
0.01756 
0.01757 
0.01759 
0.01761 


5.452 
5325 
5204 
5.089 
4.979 


5.470 
5343 
5222 
5.107 
4.997 


281.90 
283.67 
285.42 
287.13 
288.80 


900.5 
8992 
897.9 
896.7 
895.4 


1182.4 
1182.9 
1183.4 
1183.8 
11842 


0.4532 
0.4555 
0.4578 
0.4599 
0.4621 


1.1670 
1.1627 
1.1586 
1.1545 
1.1505 


1.6202 
1.6182 
1.6163 
1.6144 
1.6126 


80.0 
82.0 
84.0 
86.0 
88.0 


90.0 
92.0 
94.0 
96.0 
98.0 


32027 
321.83 
32337 
324.88 
32637 


0.01763 
0.01764 
0.01766 
0.01768 
0.01769 


4.874 
4.773 
4.676 
4384 
4.494 


4.892 
4.791 
4.694 
4.602 
4.512 


290.45 
292.07 
293.67 
29525 
1296.80 


8942 
893.0 
891.8 
890.6 
889.4 


1184.6 
1185.0 
1185.4 
1185.8 
1186.2 


0.4642 
0.4663 
0.4683 
0.4703 
0.4723 


1.1465 
1.1427 
1.1389 
1.1352 
1.1316 


1.6107 
1.6090 
1.6072 
1.6055 
1.6038 


90.0 
92.0 
94.0 
96.0 
98.0 






28 



CHAPTER 1. AIR, WATER AND STEAM 



TABLES. PROPERTIES OF SATURATED STEAM: PRESSURE TABLE (Continued) 







Specific Volume 


Total Heat 


Entropy 




Ab*. Pr*. 
Lb./Sq. In. 


BSfe 


Sat. Sat. 
Liquid Evap. Vapor 


Sat. Sat. 
Liquid Evap. Vapor 


Liquid Evap. Vapor 


Ab*. Pr*M. 
Lb./Sq. In. 


P 


t 


Vf Vfg Vg 


hf hfg h K 


Sf Sfg Sff 


P 


100.0 


327.83 


0.01771 4.408 4.426 


29833 888.2 1186.6 


0.4742 1.1280 1.6022 


100.0 


102.0 


329.27 


0.01773 4326 4344 


299.83 887.1 1186.9 


0.4761 1.1245 1.6006 


102.0 


104.0 


330.68 


0.01774 4.247 4.265 


30130 886.0 11873 


0.4779 1.1211 1.5990 


104.0 


106.0 


332.08 


0.01776 4.171 4.189 


302.76 884.9 1187.6 


0.4798 1.1177 1.5974 


106.0 


108.0 


333.44 


0.01777 4.097 4.115 


304.19 883.8 1188.0 


0.4816 1.1144 1.5959 


108.0 


110.0 


334.79 


0.01779 4.026 4.044 


305.61 882.7 11883 


0.4834 1.1111 1.5944 


110.0 


112.0 


336.12 


0.01780 3.958 3.976 


307.00 881.6 1188.6 


0.4851 1.1079 1.5930 


112.0 


114.0 


337.43 


0.01782 3.892 3.910 


30836 880.6 1188.9 


0.4868 1.1048 1.5915 


114.0 


116.0 


338.72 


0.01783 3.828 3.846 


309.71 879.5 1189.2 


0.4885 1.1017 1.5901 


116.0 


118.0 


340.01 


0.01785 3.766 3.784 


311.05 878.5 1189.5 


0.4901 1.0986 1.5887 


118.0 


120.0 


341.26 


0.01786 3.707 3.725 


31237 877.4 1189.8 


0.4918 1.0956 1.5874 


120.0 


122.0 


342.50 


0.01788 3.652 3.670 


313.67 876.4 1190.1 


0.4934 1.0926 1.586Q 


122.0 


124.0 


343.73 


0.01789 3.597 3.615 


314.96 875.4 1190.4 


0.4950 1.0897 1.5847 


124.0 


126.0 


344.94 


0.01791 3.542 3.560 


316.23 874.4 1190.6 


0.4965 1.0868 1.5834 


126.0 


128.0 


346.14 


0.01792 3.487 3.505 


317.49 873.4 1190.9 


0.4981 1.0840 1.5821 


128.0 


130.0 


347.31 


0.01794 3.433 3.451 


318.73 872.4 1191.2 


0.4996 1.0812 1.5808 


130.0 


132.0 


348.48 


0.01795 3383 3.401 


319.95 871.5 1191.4 


0.5011 1.0784 1.5796 


132.0 


134.0 


349.64 


0.01796 3335 3353 


321.17 870.5 1191.7 


0.5026 1.0757 1.5783 


134.0 


136.0 


350.78 


0.01798 3.288 3306 


32237 869.6 1191.9 


0.5041 1.0730 1.5771 


136.0 


138.0 


351.91 


0.01799 3.242 3.260 


323.56 868.6 1192.2 


0.5056 1,0703 1.5759 


138.0 


140.0 


353.03 


0.01801 3.198 3.216 


324.74 867.7 1192.4 


0.5070 1.0677 1.5747 


140.0 


142.0 


354.14 


0.01802 3.155 3.173 


325.91 .866.7 1192.6 


0.5084 1.0651 1.5735 


142.0 


144.0 


355.22 


O.Q1804 3.112 3.130 


327.06 865.8 1192.9 


0.5098 1.0625 1.5724 


144.0 


146.0 


35631 


0.01805 3.071 3.089 


328.20 864.9 1193.1 


0.5112 1.0600 1.5712 


146.0 


148.0 


35737 


0.01806 3.031 3.049 


32932 864.0 11933 


0.5126 1.0575 1.5701 


148.0 


150.0 


358.43 


0.01808 2.992 3.0'10 


330.44 863.1 1193.5 


0.5140 1.0550 1.5690 


150.0 


152.0 


359.47 


0.01809 2.954 2.972 


331.54 862.2 1193.7 


0.5153 1.0526 1.5679 


152.0 


154.0 


360.51 


0.01810 2.917 2.935 


332.64 8613 1193.9 


0.5166 1.0502 1.5668 


154.0 


156.0 


361.53 


0.01812 2.882 2.9QO 


333.72 860.4 1194.1 


0.5180 1.0478 1.5658 


156.0 


158.0 


362.54 


0.01813 2.846 2.864 


334.80 859.5 11943 


0.5193 1.0454 1.5647 


158.0 


160.0 


363.55 


0.01814 2.812 2.830 


335.86 858.7 1194.5 


0.5205 1.0431 1.5636 


160.0 


162.0 


364.54 


0.01816 2.779 2.797 


336.91 857.8 1194.7 


0.5218 1.0408 1.5626 


162.0 


164.0 


365.52 


0.01817 2.746 2.764 


337.95 857.0 1194.9 


0.5230 1.0385 1.5616 


164.0 


166.0 


366.50 


0.01818 2.715 2.733 


338.99 856.1 1195.1 


0.5243 1.0363 1.5606 


166.0 


168.0 


367.46 


0.01819 2.683 2.701 


340.01 855.2 11953 


0.5255 1.0340 1.5596 


168.0 


170.0 


368.42 


0.01821 2.653 2.671 


341.03 854.4 1195.4 


0.5268 1.0318 1.5586 


170.0 


172.0 


369.37 


0.01822 2.623 2.641 


342.04 853.6 1195.6 


0.5280 1.0296 1.5576 


172.0 


174.0 


370.31 


0.01823 2.594 2.612 


343.04 852.7 1195.8 


0.5292 1.0275 1.5566 


174.0 


176.0 


371.24 


0.01825 2.566 2.584 


344.03 851.9 1196.0 


0.5304 1.0253 1.5557 


176.0 


178.0 


372.16 


0.01826 2.538 2.556 


345.01 851.1 1196.1 


0.5315 1.0232 1.5548 


178.0 


180.0 


373.08 


0.01827 2.511 2.529 


345.99 8503 1196.3 


0.5327 1.0211 1.5538 


180.0 


182.0 


374.00 


0.01828 2.484 2.502 


346.97 849.5 1196.4 


0.5339 1.0190 1.5529 


182.0 


184.0 


374.90 


0.01829 2.458 2.476 


347.94 848.6 1196.6 


0.5350- 1.0169 1.5520 


184.0 


186.0 


375.78 


0.01831 2.433 2.451 


348.89 847.9 1196.8 


0.5362 1.0149 1.5511 


186.0 


188.0 


376.67 


0.01832 2.407 2.425 


349.83 847.1 1196.9 


0.5373 1.0129 1.5502 


188.0 


190.0 


377.55 


0.01833 2383 2.401 


350.77 8463 1197.0 


0.5384 1.0109 1.5493 


190.0 


192.0 


378.42 


0.01834 2359 2377 


351.70 845.5 1197.2 


0.5395 1.0089 1.5484 


192.0 


194.0 


379.27 


0.01835 2335 2353 


352.61 844.7 11973 


0.5406 1.0070 1.5475 


194.0 


196.0 


380.13 


0.01837 2312 2330 


353.53 844.0 1197.5 


0.5417 1.0050 1.5467 


196.0 


198.0 


380.97 


0:01838 2.289 2307 


354.43 843.2 1197.6 


0.5427 1.0031 1.5458 


198.0 


200.0 


381.82 


0.01839 2.267 2.285 


35533 842.4 1197.8 


0,5438 1.0012 1.5450 


200.0 


205.0 


383.89 


0.01842 2.213 2.231 


357.56 840.5 1198.1 


0.5465 0.9964 1.5429 


205.0 


210.0 


385.93 


0.01844 2.162 2.180 


359.76 838.6 1198.4 


0.5491 0.9918 1.5409 


210.0 


215.0 


387.93 


0.01847 2.113 2.131 


361.91 836.8 1198.7 


0.5516 0.9873 1.5389 


215.0 


220.0 


389.89 


0.01850 2.066 2.084 


364.02 835.0 1199.0 


0.5540 0.9829 1.5369 


220.0 


225.0 


391.81 


0.01853 2.0208 2.0393 


366.10 833.2 11993 


0.5565 0.9786 1.5350 


225.0 


230.0 


393.70 


0.01856 1.9778 1.9964 


368.14 831.4 1199.6 


0.5588 0.9743 1.5332 


230.0 


235.0 


395.56 


0.01859 1.9367 1.9553 


370.15 829.7 1199.8 


0.5612 0.9702 15313 


235.0 


240.0 


397.40 


0.01861 1.8970 1.9156 


372.13 827.9 1200.1 


0.5635 0.9661 1.5295 


240.0 


246.0 


399.20 


0.01864 1.8589 1.8775 


374.09 826.2 12003 


0,5658 0.9620 1.5278 


245.0 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 


TABLE 8. PROPERTIES OF SATURATED STEAM: PRESSURE TABLE (Concluded) 






Specific Volume 


Total Heat 


Entropy 




AW. Pr*. 


Trop. 


Sat. Sat. 


Sat. Sat. 


Sat. Sat. 


Ab. Pratt. 


Lb.,Sq. In. 


D*t> F. 


Liquid Evap. Vapor 


Liquid Evap. Vapor 


Liquid Evap. Vapor 


Lb./Sq. In. 


P 


t 


Vf Vf* Vg 


hf hfg hg 


Sf Sfg Sg 


P 


260.0 


400.97 


0.01867 1.8223 1.8410 


376.02 824.5 12003 


0.5680 0.9581 1.5261 


260.0 


260.0 


404.43 


0.01872 1.7536 1.7723 


379.78 821.2 1201.0 


0.5723 0.9504 1.5227 


260.0 


270.0 


407.79 


0.01877 1.6895 1.7083 


383.44 818.0 1201.4 


0.5765 0.9430 13194 


270.0 


280.0 


411.06 


0.01882 1.6302 1.6490 


387.02 814.7 1201.8 


0.5805 0.9357 1.5163 


280.0 


290.0 


41454 


0.01887 1.5745 13934 


390.50 811.6 1202.1 


0.5845 0.9287 13132 


290.0 


300.0 


41733 


0.01892 1.5225 1.5414 


393.90 808.5 1202.4 


03883 0.9220 13102 


300.0 


320.0 


42359 


0.01901 1.4279 1.4469 


400.47 8023 1203.0 


0.5957 0.9089 1.5046 


320.0 


340.0 


428.96 


0.01910 13439 13630 


406.75 796.6 1203.4 


0.6027 0.8965 1.4992 


340.0 


360.0 


434.39 


0.01918 15689 15881 


412.80 790.9 1203.7 


0.6094 0.8846 1.4940 


360.0 


380.0 


439.59 


0.01927 15015 15208 


418.61 7853 1203.9 


0.6157 0.8733 1.4.891 


380.0 


400.0 


444.58 


0.0194 1.1407 1.1601 


4245 779.8 1204.1 


0.6218 0.8625 1.4843 


400.0 


420.0 


44938 


0.0194 1.0853 1.1047 


429.6 774.5 1204.1 


0.6277 0.8520 1.4798 


420.0 


440.0 


454.01 


0.0195 1.0345 1.0540 


434.8 7693 1204.1 


0.6334 0.8420 1.4753 


440.0 


460.0 


458.48 


0.0196 0.9881 1.0077 


439.9 764.1 1204.0 


0.6388 0.8322 1.4711 


460.0 


480.0 


462.80 


0.0197 0.9456 0.9633 


444.9 759.0 1203.9 


0.6441 0.8228 1.4670 


480.0 


600.0 


466.99 


0.0198 0.9063 0.9261 


449.7 754.0 1203.7 


0.6493 0.8137 1.4630 


600.0 


620.0 


471.05 


0.0198 0.8701 0.8899 


454.4 749.0 1203.5 


0.6543 0.8048 1.4591 


520.0 


640.0 


474.99 


0.0199 0.8363 0.8562 


459.0 744.1 12035 


0.6592 0.7962 1.4554 


640.0 


660.0 


478.82 


0.0200 0.8047 0.8247 


463.6 7393 1202.9 


0.6639 0.7878 1.4517 


660.0 


680.0 


482.55 


0.0201 0.7751 0.7952 


468.0 734.5 1202.5 


0.6686 0.7796 1.4482 


680.0 


600.0 


486.17 


0.0202 0.7475 0.7677 


4723 729.8 1202.1 


0.6731 0.7716 1.4447 


600.0 


620.0 


489.71 


0.0202 0.7217 0.7419 


476.6 725.1 1201.7 


0.6775 0.7638 1.4413 


620.0 


640.0 


493.16 


0.0203 0.6972 0.7175 


480.8 7203 12015 


0.6818 0.7562 1.4380 


640.0 


660.0 


496.53 


0.0204 0.6744 0.6948 


484.9 715.9 1200.8 


0,6861 0.7487 1.4348 


660.0 


680.0 


49932 


0.0205 0.6527 0.6732 


488.9 7113 12005 


0.6902 0.7414 1.4316 


680.0 


700.0 


503.04 


0.6206 0.6321 0.6527 


492.9 706.8 1199.7 


0.6943 0.7342 1.4285 


700.0 


720.0 


506.19 


0.0206 0.6128 0.6334 


496.8 702.4 11995 


0.6983 0.7272 1.4255 


720.0 


740.0 


509.28 


0.0207 03944 0.6151 


500.6 697.9 1198.6 


0.7022 0.7203 1.4225 


740.0 


760.0 


51230 


0.0208 0.5769 03977 


504.4 693.5 1198.0 


0.7060 0.7136 1.4196 


760.0 


780.0 


51557 


0.0209 0.5602 03811 


5085 689.2 1197.4 


0.7098 0.7069 1.4167 


780.0 


800.0 


518.18 


0.0209 0.5444 03653 


511.8 684.9 1196.7 


0.7135 0.7004 1.4139 


800.0 


820.0 


521.03 


0.0210 03293 03503 


5153 680.6 1196.0 


0.7171 0.6940 1.4111 


S20.0 


840.0 
860.0 


523.83 
526.58 


0.0211 03149 0.5360 
0.0212 03013 03225 


519.0 676.4 1195.4 
522.6 672.1 1194.7 


0.7207 0.6877 1.4084 
0.7242 0.6815 1.4057 


840.0 
860.0 


880.0 


52959 


0.0213 0.4881 03094 


526.0 667.9 1194.0 


0.7277 0.6754 1.4031 


880.0 


900.0 
920.0 
940.0 
960.0 
980.0 


531.95 
534.56 
537.13 
539.66 
542.14 


0.0213 0.4756 0.4969 
0.0214 0.4635 0.4849 
0.0215 0.4520 0.4735 
0.0216 0.4409 0.4625 
0.0217 0.4303 0.4520 


5293 663.8 11933 
532.9 659.7 1192.6 
5365 655.6 1191.8 
539.6 651.5 1191.1 
542.8 647.5 11903 


0.7311 0.6694 1.4005 
0.7344 0.6635 1.3980 
0.7377 0.6577 1.3954 
0.7410 0.6520 1.3930 
0.7442 0.6464 1.3905 


900.0 
920.0 
940.0 
960.0 
980.0 


1000.0 
1060.0 
1100.0 
1160.0 
1200.0 


544.58 
55033 
55658 
561.81 
567.14 


0.0217 0.4202 0.4419 
0.0219 03960 0,4179 
0.0222 03738 03960 
0.0224 03540 03764 
0.0226 03356 03582 


546.0 643.5 1189.6 
554.0 633.6 1187.6 
561.7 623.9 1185.6 
5695 6143 1183.5 
576.5 604.9 1181.4 


0.7473 0.6408 13881 
0.7550 0.6273 13822 
0.7624 0.6141 1.3765 
0.7695 0.6014 13709 
0.7764 03891 13656 


1000.0 
1060.0 
1100.0 
1160.0 
1200.0 


1260.0 
1300.0 
1360.0 
1400.0 
1460.0 


57230 
57732 
58251 
586.96 
591.58 


0.0228 03187 03415 
0.0230 03029 03259 
0.0232 05884 03116 
0.0235 05748 05983 
0.0237 05621 05858 


583.6 595.6 1179.2 
590.6 5863 1177.0 
597.5 5775 1174.7 
6043 568.1 1172.4 
611.0 559.1 1170.0 


0.7831 03772 13603 
0.7897 03654 13552 
0.7962 03540 13501 
0.8024 03428 1.3452 
0.8086 0.5318 13404 


1260.0 
1300.0 
1360.0 
1400.0 
1460.0 


1500.0 
1600.0 
1700.0 
1800.0 
1900.0 


5964)8 
604.74 
612.98 
620.86 
62839 


0.0239 05502 05741 
0.0244 05284 05528 
0.0249 05089 0.2338 
0.0254 0.1913 05167 
0.0260 0.1754 05014 


617.5 5505 1167.6 
6305 532.6 1162.7 
6423 515.0 1157.5 
654.7 4975 115L8 
666.8 478.9 1145.7 


0.8146 0:5212 13357 
0.8262 0.5003 13265 
0.8373 0.4801 13174 
0.8482 0.4601 13083 
0.8589 0.4402 15990 


1600.0 
1600.0 
1700.0 
1800.0 
1900.0 


ooooo 


635.6 
6495 
661.9 
673.8 
684.9 


0.0265 0.1610 0.1875 
0.0277 0.1346 0.1623 
0.0292 0.1112 0.1404 
0.0310 0.0895 0.1205 
0.0333 0.0688 0.1021 


679.0 460.0 1139.0 
703.7 420.0 1123.8 
729.4 376.4 1105.8 
756.7 327.8 10843 
786.7 2723 1058.9 


0.8696 0.4200 15896 
0.8912 03788 15700 
0.9133 03356 15488 
0.9364 05892 15257 
0.9618 05379 1.1996 


2000.0 
2200.0 
2400.0 
2600.0 
2800.0 


3000.0 
3200.0 
3226.0 


6955 
704.9 
706.1 


0.0367 0,0477 0.0844 
O.C459 0.0142 0.0601 
0.0522 0.0522 


823.1 202.5 1025.6 
887.0 75.9 962.9 
925.0 925.0 


0.9922 0.1754 1.1676 
1.0461 0.0651 1.1112 
1.0785 1.0785 


3000.0 
3200.0 
3226.0 



- 30 



CHAPTER 1. AIR, WATER AND STEAM 



responding change in the latent heat of evaporation. These values are 
given in Table 8. 

Specific Heat. The specific heat of water, or the amount of heat (Btu) 
required to raise the temperature of one pound of water one degree Fahren- 
heit, varies with the temperature, but it is commonly assumed to be 
unity at all temperatures. Steam tables are based on exact values, 
however. The specific heat of ice at 32 F is 0.492 Btu per pound. The 
amount of heat required to raise one pound of water at 32 F through a 
known temperature interval depends on the average specific heat for the 
temperature range. 

Sensible and Latent Heat. The heat necessary to raise the temperature 
of one pound of water from 32 F to the boiling point is known as the heat 
of the liquid or sensible heat. When more heat is added, the water begins 
to evaporate and expand at constant temperature until the water is 
entirely changed into steam. The heat thus added is known as the latent 
heat of evaporation. 

PROPERTIES OF STEAM 

Steam is water vapor which exists in the vaporous condition because 
sufficient heat has been added to the water to supply the latent heat of 
evaporation and change the liquid into vapor. This change in state takes 
place at a definite and constant temperature which is determined solely 
by the pressure of the steam. The volume of a pound of steam is the 
specific volume which decreases as the pressure increases. The reciprocal 
of this, or the weight of steam per cubic foot, is the density. (See Table 8.) 

Steam which is in contact with the water from which it was generated is 
known as saturated steam. If it contains no actual water in the form of 
mist or priming, it is called dry saturated^ steam. If this be heated and the 
pressure maintained the same as when it was vaporized, its temperature 
will increase and it will become super-heated, that is, its temperature will 
be higher than that of saturated steam at the same pressure. 

REFERENCES 

Temperature of Evaporation, by W. H. Carrier (A.S.H.V.E. TRANSACTIONS, Vol. 24, 
1918, p. 25). 

The Evaporation of a Liquid into a Gas, by W. K. Lewis (A.S.M.E. Transactions, 
Vol. 44, 1922). 

The Evaporation of a Liquid into a Gas a Correction, by W. K. Lewis (Mechanical 
Engineering, September, 1933). 

Temperature of Evaporation of Water into Air, by W. H. Carrier and D. C. Lindsay 
(A.S.M.E. Transactions, Vol. 46, 1924). 

A New Psychrometric or Humidity Chart, by C. A. Bulkeley (A.S.H.V.E. TRANS- 
ACTIONS, Vol. 32, 1926, p. 163). 

A Review of Psychrometric Charts, by C. O. Mackey (Heating and Ventilating, 
June, July, 1931). 

Air Conditioning Applied to Cold Storage and a New Psychrometric Chart, by C, A. 
Bulkeley (Refrigerating Engineering, February, 1932). 

The Psychrometric Chart, by E. V. Hill (Aerologist, April, May, June, 1932). 

Air Conditioning Theory, by John A. Goff (Refrigerating Engineering, January, 1933). 

Mixtures of Air and Water Vapor, by C. A. Bulkeley (Refrigerating Engineering, 
January, 1933). 

31 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

Basic Theory of Air Conditioning, by Lawrence Washington (Western Conference on 
Air Conditioning, San Francisco, Calif., February 9-10, 1933). 

The Theory of the Psychrometer, by J. H. Arnold (Physics, July, September, 1933). 

Heat Transmission in Cooling Air with Extended Surfaces, by W. L. Knaus (Refrigera- 
ting Engineering, Januar> T , February, 1935). 

A New Psychrometric Chart, by F. 0. Urban (Refrigerating Engineering, November 
1935). 

Psychrometric Charts, by Donald B. Brooks (U. S. Bureau of Standards Miscellaneous 
Publication No. 143). 

The Deviation of the Actual Wet-Bulb Temperature from the Temperature of 
Adiabatic Saturation, by David Dropkin (Cornell University Engr. Exp. Station Bui. 
No. 23, July, 1936). 



PROBLEMS IN PRACTICE 

1 Given air at 70 F dry-bulb and 50 per cent relative humidity with a baro- 
metric pressure of 29.00 in. Hg, find the weight of vapor per pound of dry air. 

Pressure of saturated vapor - e t = 0.7387 in. Hg (Table 6). 
From Equation 5a, 

0.5 X 0.7387 \ 

- (0.5) X (0.7387)7 

W = 0.008024 lb of vapor per pound of dry air at 70 F dry-bulb and 50 per cent 
relative humidity. 

Approximate Method: 

Weight of saturated vapor per pound of dry air = Wt = 0.01574 lb (Table 6). 0.01574 
X 0.5 = 0.00787 lb of vapor per pound of dry air at 70 F dry-bulb and 50 per cent relative 
humidity. 

2 Given ah- with a dry-bulb temperature of 80 F, relative humidity of 55 per 
cent, and a barometric pressure of 28.85 in. Hg, calculate the weight of a cubic 
foot of mixture. 

Pressure of saturated vapor at 80 F = e t = 1.0316 in. Hg (Table 6). 
Pressure of the vapor in the mixture - 1.0316 X 0.55 = 0.5676 in. Hg. 
Pressure of the dry air in the mixture = 28.85 - 0.5676 = 28.282 in. Hg. 



__ 28.282 

~ 0.753 X 540 - 06955 lb = weight of dry air in 1 cu ft of the mixture. 

Likewise from Equation 4a, 



^ = 1.21 X 540 = 0-W0868 lb - weight of vapor per cubic foot at 55 per cent 
relative humidity. 
Weight of 1 cu ft of the mixture = 0.06955 + 0.000868 = 0.070418 lb. ' 

3 Given air with a dry-bulb temperature of 75 F, a relative humidity of 60 per 
cent, and a barometric pressure of 28.80 in. Hg, calculate the volume of 1 lb of 

ine mixture. 

Pressure of saturated vapor at 75 F = e t === 0.8745 in. Hg. 
Pressure of vapor in the mixture = 0.8745 X 0.6 ~ 0.525 in. Hg. 
Pressure of dry air in the mixture 28.80 - 0.525 - 28.275 in. Hg. 

32 



CHAPTER 1. AIR, WATER AND STEAM 



^ = ______ 28.275 _ = 0.07018 Ib = weight of dry air in 1 cu ft of the mixture. 

0.753 X 535 

From Equation 4a, 

j _ Q * 525 _ = 000811 Ib = weight of vapor per cubic foot at 55 per cent 

** " 1.21 X 535 
relative humidity. 
Weight of 1 cu ft of the mixture = 0.07018 -f 0.000811 = 0.070991 Ib. 

Volume of 1 Ib of the mixture = -Q^ggf = 14 - 08 cu ft - 



4 It is desired to maintain a temperature of 80 F and a relative humidity of 
^ per cent in a factory where the equipment gives off 6,000 Btu per hour If 
thf entering ah- is at 70 F with an average barometric pressure of 29.92 m. Hg, 
determSe the relative humidity, and the pounds of an: required pex -hour *f 
there is no heat interchange between the walls, windows, or floors of the 
building. 

Pressure of saturated vapor at 80 F = 1.0316 in. Hg (Table 6). 
Pressure of vapor in the mixture - 1.0316 X 0.5 = 0.5158 in. Hg. 

IF = 0-622 ( ^S^ )= 0.01091 Ib. 

Pressure of saturated vapor at 70 F 0,7387 in. Hg. 

With the same specific humidity 

/ 0.7387 X 
0.01091 - 0.622 ( 29 . 92 



$ = 69.8 per cent relative humidity at 70 F. , 

h = 24 X 80 + 0.01091 [1059.2 + (0.45 X 80)] = 31.15 Btu per pound, the heat con- 
tent of the mixture at 80 F and 50 per cent relative humidity. 

h = 24 X 70 + 0.01091 [1059.2 + (0.45 X 70)] = 28.70 Btu per pound, the heat con- 
tent of the mixture at 70 F and the same specific humidity. 
31.15 28.70 = 2.45 Btu to be removed per pound of air. 
6000 Btu = heat given off by equipment per hour. 



6000 
2.45 



= 2449 Ib of air required per hour. 



. 

remains constant, what will be the new pressure, P 2 , in in. Hg? 



PV = w(* 

R (for air) = 53.34. 

W = 1 Ib. 

P = absolute pressure, pounds per square foot. 
1 X 53.34 X (78 + 460) 

/ " 29.92 X 0.491 X 144 

V = 13.57 cu ft = volume of 1 Ib. 

P* _ T* p - T * P * 

Pi - 3\ ; 2 Ti 

v . (96 + 460) (29.92 X 0.491 X 144) = 3Q M .^ Hg 

^2 - ( 7g + 460 ) (0.491 X 144) 



including the heat content of the liquid above 32 F. 

33 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

From Equation 12, 

h = 0.24 ft - 0) + Wh+ 
where 

h s 1059.2 + 0.45*' (Empirical equation derived from Keenan's Steam Tables). 

/' = 75 F. 
W 0.01873 Ib of water vapor (Table 6). 

h - 0.24 (75 - 0) -f 0.01873 [1059.2 + (0.45 X 75)]. 

h = 38.46 Btu per pound of dry air. 

7 A building requires 50,000 cu ft of air per hour to be raised from 10 F 
dry-bulb and 75 per cent relative humidity to 72 F dry-bulb and 30 per cent 
relative humidity. Determine the amount of heat and the weight of water 
which it is necessary to supply per hour if the temperature of the supply water 
is 50 F and the barometric pressure is 28.75 in. Hg. 

Assume air volume to be dry air at 70 F. 

Weight of air 0.075 X 50,000 - 3750 Ib per hour. 

From Table 6, 

Pressure of vapor in the mixture, outside air = 0.75 X 0.0221 = 0.0166 in. Hg. 

Specific humidity, outside air - 0.622 ( 2 g 75 '- cfoiee ) " - 0003589 Ib> 

From Table 6, 

Pressure of vapor in the mixture, inside air = 0.30 X 0.7906 = 0.2372 in. Hg. 

Specific humidity, inside air = 0.622 ( 2 g 75^ 3 Q 237is) = ao05174 lb - 
Water to be added = 3750 (0.005174 - 0.0003589 ) = 18.06 lb per hour. 

Heat content, inside air = 0.24 X 72 -f 0.005174 [1059.2 + (0.45 X 72)] - 22.925 Btu 
per pound. 

Heat content, outside air 0.24 X (-10) -f- 0.0003589 [1059.2 -f (0.45 X -10)] = 
-2.021 Btu per pound. 

Btu added incident to the water per pound of dry air. 

(0.005174 - 0.0003589) (50 - 32) = 0.0867 Btu per pound. 

Heat requirement per hour = [22.925 - (-2.021 + 0.0867)] X 3750 = 93,221 Btu. 

8 Determine the amount of heat and water that must be extracted to cool 
3750 lb of air (weighed dry) from 95 F and 60 per cent relative humidity to 50 F 
and 100 per cent relative humidity with a barometric pressure of 28.75 in. Hg. 

Pressure of vapor in the mixture, outside air = 0.6 X 1.659 = 0.995 in. Hg. 

Specific humidity, outside air = 0.622 [ no >., ^ Mtf } = 0.0223 lb. 

\28.7o 0.995 / 
Specific humidity, inside air - 0.007626 lb. 

Weight of water to be extracted per hour = (0.0223 - 0.007626) X 3750 = 55.03 lb. 

Heat content, outside air = 0.24 X 95 + 0.0223 [1059.2 -f (0.45 X 95)] - 47.37 Btu 
per pound. 

Heat content, inside air - 0.24 X 50 -h 0.00764 [1059.2 + (0.45 X 50)] = 20.26 Btu 
per pound. 

Heat to be extracted = (47.37 - 20.26) X 3750 = 101,662 Btu. 



34 



Chapter 2 

REFRIGERANTS AND AIR DRYING AGENTS 



Properties o Refrigerant Substances, Selection Fact r ^olid 

Adsorbents, Liquid Absorbents, Nature o Processes, Tempera- 

ture Pressure Concentration Relations 



BOTH cooling and dehumidification of air are usually desirable at 
certain times. Cooling may be regarded as the extraction of sensible 
heat while dehumidification necessitates the removal of patent heat. By 
a suitable selection and combination of methods M*^***^^ 
processes may be accomplished simultaneously or they ^^6 secured 
independent of each other and at different times as desired On occasion 
the desired result can be secured by extracting sensible heat only while 
in other cases drying alone will produce the end conditions sought. 
SuiSble substances must be available for use in every particular case 
Generally, when both cooling and dehumidification are fO"^ current 
oractice makes use of artificially produced refrigeration in some forrn^ 

air conditioning work. Little mention is made here f methods, i y stems 
or equipment whereby these substances may be applied, which mtor 
mation may be found in Chapter 24. 

REFRIGERANTS 

Since air cooling and dehumidification are frequently Accomplished by 
evaoorating a liquid under circumstances which will permit the neat 
necSSrv to be Sracted from the air, the refrigerants are substances 

Considerations including availability, cost, safety chemical stability and 
adaptability to the type of refrigerating system to be used. 

In this chapter detailed consideration is limited to six substances viz 
ammonia, carbon dioxide, dichlorodiftuoromethane (P 12 ), methyl 



35 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 1. PROPERTIES OF AMMONIA 



HEAT CONTENT AND ENTROPY TA.KEN FROM 40 F 



T ^ p< Ln PER Heat Content 
t So Is. 


Entropy 


100 F Superhea 


200 F Superheat 




i Liquid , Vapor , Liquid 


Vapor 


Liqui 


Vapo 


Ht.C 


Entro 


Ht. C 


Entropy 


, 30.42 0.0241 


? 9.116 


42 


611. i 


30.097 


1.335 


666 


1.443 


720 


1.5317 


2 31.92:0.0242 


4 8.714 


45 


612.' 


tO. 102 


1.331 


667 


1.440( 


721 


1.5277 


4 j 33 .47, ; 0.02430 8.333 


47 


613. ( 


)0.106 


1.327 


668 


1.436 


722 


1.5236 


5 34. 27*0.02432 8.150 \ 48 


613.; 


50.109 


1.325 


668 


1.434 


722 


1.5216 


6 35.09 0.02435 7.971 ! 49 


613. < 


50.111 


1.323 


669 


1.432 


723 


1.5196 


8 , 36.77 0.02440 7.629 


51 


614.; 


JO. 116 


1.319 


670 


1.428 


724 


1.5155 


10 38.51 0.0244< 


S 7.304 


53 


614. < 


J0.120 


1.315 


670. 


1.424 


725 


1.5115 


12 40.3l! 0.0245] 


I 6.996 


56. 


615.* 


J0.125 


1.311 


671. 


1.420 


725 


1.5077 


14 42.180.0245' 


" 6,703 


58. 


616.1 


0.130C 


1.308 


672. 


1.416 


726. 


1.5039 


16 44.12 0.02462 6.425 


60. 


616. e 


> 0.134 


1.304 


673. 


1.413 


727. 


1.5001 


18 


46.13 0.02465 


J 6.161 


62. 


617.2 


10.139 


1.300 


674. 


1.409 


728. 


1 .4963 


20 


48.2110.02474 5.910 


64. 


617. 


0.143 


1.296 


675. 


1.405 


729. 


1.4925 


22 


50.36 0.0247S 


> 5.671 


66. 


618. 


0.148 


1.293 


675. 


1.402 


730. 


1 .4889 


24 


52.59 0.0248 


5.443 


69. 


618. 


0.152 


1.289 


676. 


1.398 


731. 


1.4853 


26 


54.90, 0.0249 


5.227 


71. 


619. 


0.157 


1.286 


677. 


1.395 


732. 


1 .4816 


28 


57.28 0.0249 


5.021 


73. 


619. 


0.161 


1.282 


678. 


1.391 


733. 


1 .4780 


30 


59.74i 0.0250 


4.825 


75. 


620. 


0.166 


1.279 


678. 


1.387 


734. 


1.4744 


32 


62.291 0.0250 


4.637 


77. 


621. 


0.170 


1.275 


679. 


1.384 


735. 


1.4710 


34 


64.91 


0.0251 


4.459 


80. 


621. 


0.175 


1.272 


680. 


1.381 


736. 


1.4676 


36 


67.63 


1 0.0252 


4.289 


82. 


622. 


0.179 


1.268 


681. 


1.377 


736. 


1.4643 


38 


70.4310.0252 


4.126 


84. 


622. 


0.184 


1.2652 


681. 


1.374 


737. 


1.4609 


39 71.8710.0253 


4.048 


85. 


622. 


0.186 


1.2635 


682. 


1.372 


738. 


1.4592 


40 j 73.32 0.0253 


3.971 


86. 


623. 


0.1885 


1.2618 


682. 


1.3712 


738. 


1.4575 


41 


74. 80j 0.0253 


3.897 


87. 


623. 


0.1908 


1.2602 


683. 


1.3696 


739.0 


1.4559 


42 


76.31 


0.02539 


3.823 


89.0 


623.4 


0.1930 


1.2585 


683.4 


1.3680 


739.5 


1.4542 


44 


79.38 


0.02545 


3.682 


91.2 


623.9 


0.1974 


.2552 


684.2 


1.3648 


740 4 


.4510 


46 


82.55 


0.0255 


3.547 


93.5 


624.4 


0.2018 


.2519 


684.9 


.3616 


741.3 


.4477 


48 


85.82 


0.02558 


3.418 


95.7 


624.8 


0.2062 


.2486 


685.6 


.3584 


742 2 


.4445 


50 


89.19 


0.02564 


3.294 


97.9 


625.2 


0.2105 


.2453 


686.4 


.3552 


743.1 


.4412 


52 


92.66 


0.02571 


3.176 


100.2 


625.7 


0.2149 


.2421 


687.1 


.3521 


744.0 


!4382 


54 


96.23 


0.02577 


3.063 


102.4 


626.1 


0.2192 


.2389 


687.8 


.3491 


744.8 


.4351 


56 


99.91 


0.02584 


2.954 


104.7 


626.5 


0.2236 


.2357 


688.5 


.3460 


745.7 


.4321 


58 


103.7 


0.02590 


2.851 


106.9 


626.9 


0.2279 


.2325 


689.2 


.3430 


746 5 


4290 


60 
62 


107.6 
111.6 


0.02597 
0.02604 


2.751 
2.656 


109.2 
111.5 


627.3 
627.7 


0.2322 
0.2365 


.2294 
.2262 


689.9 
690.6 


.3399 
.3370 


747.4 
748.2 


.'4260 
4231 


66 
68 
70 
72 
74 
76 
78 
80 
82 
84 
86 
88 
90 
92 
94 
96 
98 
100 
102 ; 


115.7 
120.0 
124.3 
128.8 
133.4 
138.1 
143.0 
147.9 
153.0 
158.3 
163.7 
169.2 
174.8 
180.6 
186.6 
192.7 
198.9 
205.3 
211.9 
218.6 


0.02611 
0.02618 
0.02625 
0.02632 
0.02639 
0.02646 
0.02653 
0.02661 
0.02668 
0.02675 
0.02684 
0.02691 
0.02699 
0.02707 
0.02715 
0.02723 
0.02731 
0.02739 
0.02747 
0.02756 


2.565 
2.477 
2.393 
2.312 
2.235 
2.161 
2.089 
2.021 
1.955 
1.892 
1.831 
1.772 
1.716 
1.661 
1.609 
1.559 
1.510 
1,464 
1.419 
1.375 


113.7 
116.0 
118.3 
120.5 
122.8 
125.1 
127.4 
129.7 
132.0 
134.3 
136.6 
138.9 
141.2 
143.5 
145.8 
148.2 
150.5 
152.9 
155.2 
157.6 


628.0 
628.4 
628.8 
629.1 
629.4 
629.8 
630.1 
630.4 
630.7 
631.0 
631.3 
631.5 
631.8 
632.0 
632.2 
632.5 
632.6 
632.9 
633.0 
633.2 


0.2408 
.2451 
.2494 
.2537 
.2579 
.2622 
.2664 
.2706 
.2749 
.2791 
.2833 
.2875 
.2917 
.2958 
.3000 
.3041 
.3083 
.3125 
.3166 
.3207 


.2231 
.2201 
.2170 
.2140 
.2110 
2080 
2050 
2020 
1991 
1962 
1933 
1904 
1875 
1846 
1818 
1789 
1761 
1733 
1705 
1677 


691.3 
691.9 
692.6 
693.3 
694.0 
694.6 
695.3 
695.9 
696.6 
697.2 
697.8 
698.5 
99.1 
99.7 
00.3 
00.9 
01.5 
02.1 
02.7 
03.3 


.3341 
.3312 
.3283 
.3254 
.3226 
.3199 
.3171 
.3144 
.3116 
.3089 
3063 
3040 
3010 
2983 
2957 
2932 
2906 
2881 
2855 
2830 


749.1 
749.9 
750.8 
751.6 
752.4 
753.3 
754.1 
755.0 
755.8 
756.6 
757.4 
758.3 
759.1 
759.9 
760.7 
61.5 
62.2 
63.0 
63.8 
64.6 


.4202 
.4172 
.4143 
.4114 
.4086 
.4059 
.4031 
.4004 
3976 
3949 
3923 
3896 
3870 
3843 
3818 
3793 
3768 
3743 
3718 
3693 



36 



CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS 



TABLE 1. PROPERTIES OF AMMONIA (Continued) 









HEAT CONTENT AND ENTROPY TAKEN FROM -40 F 


o.m 


ABB 


. 




oAT. 

TEMP. 

F 


PRESS. 
LB PER 

SQlN. 


V OLUME 


Heat Content 


Entropy 


100 F Superheat 


200 F Superheat 






Liquid 


Vapor 


Liquid 


Vapor 


Liquid 


Vapor 


Ht. Ct. 


Entropy 


Ht. Ct. 


Entropy 


104 


225.4 


0.0276* 


1.334 


159.9 


633.4 


0.3248 


1.1649 


703.8 


1.2805 


765.3 


1.3668 


106 


232.5 


0.02773 


1.293 


162.3 


633.5 


0.3289 


1.1621 


701.3 


1.2780 


766.1 


1.3643 


108 


239.7 


0.02782 


1.254 


164.6 


633.6 


0.3330 


1.1593 


705.0 


1.2755 


766.9 


1.3619 


110 


247.0 


0.02790 


1.217 


167.0 


633.7 


0.3372 


1.1566 


705.5 


.2731 


767.6 


1.3596 


112 


254.5 


0.02799 


1.180 


169.4 


633.8 


0.3413 


1.1538 


706.1 


.2708 


768.3 


1.3573 


114 


262.2 


0.02808 


1.145 


171.8 


633.9 


0.3453 


1.1510 


706.6 


.2684 


769.1 


1.3550 


116 


270.1 


0.02817 


1.112 


174.2 


634.0 


0.3495 


1.1483 


707.2 


.2661 


769.8 


1.3527 


118 


278.2 


0.02827 


1.079 


176.6 


634.0 


0.3535 


1.1455 


707.7 


.2636 


770.5 


1.3503 


120 


286.4 


0.02836 


1.047 


179.0 


634 


0.3576 


1.1427 


708.2 


.2612 


771.3 


1.3479 


122 


294.8 


0.02846 


1.017 


181.4 


634.0 


0.3618 


1.1400 


708.6 


.2587 


772.0 


1.3455 


124 


303.4 


0.02855 


0.987 


183.9 


634.0 


0.3659 


1.1372 


709.1 


.2563 


772.8 


1.3431 


126 


312.2 


0.02865 


0.958 


186.3 


633.9 


0.3700 


1.1344 


709.6 


1.2538 


773.5 


1.3407 


128 


321.2 


0.02875 


0.931 


188.8 


633.9 


0.3741 


1.1316 


710.0 


1.2513 


774.2 


1.3383 



chloride, water, and monofluorotrichloromethane (Fn), for each of 
which a tabl.e is presented. Each table gives the principal physical 
properties of the saturated substance,, and all are arranged in uniform 
fashion. In each case columns are included which give the heat content 
and entropy of the superheated vapor at two selected points. Tables 1, 
2, 3 and 4 which include the refrigerants much used in reciprocating and 
rotary mechanical compression systems have a 2 F temperature interval. 
As water and JPu are much used in centrifugal compression systems the 
temperature interval in Tables 5 and 6 is 5 F. 

AIR DRYING AGENTS 

Moisture may be removed from air, thus accomplishing dehumidi- 
fication, by the use of any one of a number of substances if the moist air 
and these substances are brought together under suitable circumstances. 
One class of these substances are solids at ordinary conditions and have 
the power of adsorbing the moisture from the air. Another class of air 
drying agents are liquids under ordinary conditions and absorb the mois- 
ture from the air. Nearly all the drying agents in frequent commercial 
use in air conditioning installations are of one or the other of these two 
classes. 

Adsorbents 

These substances are characterized by a physical structure containing 
a great number of extremely small pores but still retaining sufficient 
mechanical strength to resist whatever wear and handling to which they 
are subjected. To be suitable for air drying purposes they must be widely 
available at economical cost, durable in use, stable in form and properties, 
and capable of withstanding the re-activation processes by which they are 
made ready for repeated use. They must also possess capacity for 
adsorbing and holding so sufficient a quantity of moisture that the 
dimensions of the beds necessary to accommodate them will be practical. 

37 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 2, PROPERTIES OF CARBON DIOXIDE 



HEAT CONTENT AND ENTROPY TAKEN FROM 40 F 



& p *-- 

^' LB PER 
* SQ Is. 


VOLUME 


Heat Content 


Entropy 


50 F Superheat 


100 F Superheat 


Liquid Vapor 


Liquid 


1 

Vapor 


Liquid 


Vapor 


Ht. Ct. 


Entropy 


Ht. Ct. 


Entropy 





305.5 0.01570 0.29040 


18.8 


138.9 


0.0418 


0.3024 


153.7 


0.3342 


167.5 


0.3612 




315.9 


0.01579 0.28030 


19.8 


138.8 


0.0440 


0.3014 


153.7 


0.3330 


167.6 


0.3600 


4 


326.5 


0.01588 0.27070 


20.8 


138.8 


0.0461 


0.3005 


153.7 


0.3318 


167.7 


0.3588 


5 


332.0 


0.0159210.26610 


21.3 


138.8 


0.0472 


0.3000 


153.7 


0.3312 


167.7 


0.3582 


6 


337.4 


0.01596 


0.26140 


21.8 


138.7 


0.0483 


0.2994 


153.7 


0.3306 


167.8 


0.3576 


8 


348.7 


0.01605 


0.25260 


22.9 


138.7 


0.0504 


0.2982 


153.7 


0.3293 


167.9 


0.3563 


10 


360.2 


0.01614 


0.24370 


24.0 


138.7 


0.0526 


0.2970 


153.7 


0.3281 


168.0 


0.3550 


12 


371.9 


0.01623 


0.23540 


25.0 


138.6 


0.0548 


0.2958 


153.7 


0.3270 


168.1 


0.3538 


14 


383.9 


0.01632 


0.22740 


26.1 


138.6 


0.0571 


0.2946 


153.7 


0.3259 


168.2 


0,3526 


16 


396.2 


0.01642 


0.21970 


27.2 


138.5 


0.0593 


0.2933 


153.7 


0.3249 


168.3 


0.3513 


18 


408.9 


0.01652 


0.21210 


28.3 


138.4 


0.0616 


0.2921 


153.7 


0.3238 


168.5 


0.3501 


20 


421.8 


0.01663 


0.20490 


29.4 


138.3 


0.0638 


0.2909 


153.7 


0.3227 


168.6 


0.3489 


22 


434.0 


0.01673 


0.19790 


30.5 


138.2 


0.0662 


0.2897 


153.7 


0.3214 


168.7 


0.3479 


24 


448.410.01684 


0.19120 


31.7 


138.1 


0.0686 


0.2885 


153.7 


0.3202 


168.8 


0.3470 


26 


462.2 


0.01695 


0.18460 


32.9 


138.0 


0.0710 


0.2873 


153.7 


0.3189 


168.9 


0.3460 


28 


476.3 


0.01707 


0.17830 


34.1 


137.9 


0.0734 


0.2861 


153.7 


0.3177 


169.0 


0.3451 


30 


490.8 


0.01719 


0.17220 


35.4 


137.8 


0.0758 


0.2849 


153.7 


0.3164 


169.1 


0.3441 


32 


505.5 


0.01731 


0.16630 


36.7 


137.7 


0.0781 


0.2834 


153.7 


0.3158 


169.2 


0.3431 


34 


522.6 


0.01744 


0.16030 


37.9 


137.4 


0.0804 


0.2820 


153.7 


0.3151 


169.3 


0.3421 


36 


536.0 


0.01759 


0.15500 


39.1 


137.2 


0.0828 


0.2805 


153.7 


0.3145 


169.4 


0.3411 


38 


551.7 


0.01773 


0.14960 


40.4 


136.9 


0.0851 


0.2791 


153.7 


0.3138 


169.5 


0.3401 


39 


559.7 


0.01780 


0.14700 


41.0 


136.8 


0.0862 


0.2783 


153.7 


0.3135 


169.5 


0.3396 


40 i 567.8 


0.01787 


0.14440 


41.7 


136.7 


0.0874 


0.2776 


153.7 


0.3132 


169.6 


0.3391 


41 


576.0 


0.01794 


0.14185 


42.3 


136.5 


0.0887 


0.2768 


153.7 


0.3127 


169.6 


0.3386 


42 


584.3 


0.01801 


0.13930 


42.9 


136.3 


0.0899 


0.2761 


153.7 


0.3122 


169.7 


0.3381 


44 


601.1 


0.01817 


0.13440 


44.3 


136.1 


0.0924 


0.2745 


153.7 


0.3112 


169.8 


0.3371 


46 


618.2 


0.01834 


0.12970 


45.6 


135.7 


0.0950 


0.2730 


153.7 


0.3101 


169.9 


0.3362 


48 


635.710.01851 


0.12500 


47.0 


135.4 


0.0975 


0.2714 


153.7 


0.3091 


170.0 


0.3352 


50 


653.6 


0.01868 


0.12050 


48.4 


135.0 


0.1000 


0.2699 


153.7 


0.3081 


170.1 


0.3342 


52 


671.9 


0.01887 


0.11610 


49.8 


134.5 


0.1027 


0.2681 


153.7 


0.3069 


170.2 


0.3333 


54 


690.6 


0.01906 


0.11170 


51.2 


133.9 


0.1054 


0.2663 


153.7 


0.3057 


170.3 


0.3324 


56 


709.5 


0.01927 


0.10750 


52.6 


133.4 


0.1081 


0.2644 


153.7 


0.3046 


170.5 


0.3315 


58 


728.8 


0.01948 


0.10340 


54.0 


132.7 


0.1108 


0.2626 


153.7 


0.3034 


170.6 


0.3306 


60 


748.6 


0.01970 


0.09940 


55.5 


132.1 


0.1135 


0.2608 


153.7 


0.3022 


170.7 


0.3297 


62 


769.0 


0.01995 


0.09545 


57.0 


131.3 


0.1164 


0.2584 


153.7 


0.3012 


170.8 


0.3289 


64 


789.4 


0.02020 


0.09180 


58.6 


130.6 


0.1194 


0.2560 


153.7 


0.3002 


170.9 


0.3281 


66 


810.3 


0.02048 


0.08800 


60.2 


129.7 


0.1223 


0.2535 


153.7 


0.2991 


171.0 


0.3273 


68 


831.6 


0.02079 


0.08422 


61.9 


128.7 


0.1253 


0.2511 


153.7 


0.2981 


171.1 


0.3265 


70 


853.4 


0.02112 


0.08040 


63.7 


127.5 


0.1282 


0.2487 


153.7 


0.2971 


171.2 


0.3257 


72 


875.8 


0.02152 


0.07654 


65.5 


126.0 


0.1321 


0.2450 


153.7 


0.2962 


171.3 


0.3250 


74 


898.2 


0.02192 


0.07269 


67.3 


124.5 


0.1360 


0.2414 


153.7 


0.2953 


171.4 


0.3242 


76 


921.3 


0.02242 


0.06875 


69.4 


122.8 


0.1398 


0.2377 


153.7 


0.2945 


171.5 


0.3235 


78 


944.8 


0.02300 


0.06473 


71.6 


120.9 


0.1437 


0.2341 


153.7 


0.2936 


171.6 


0.3227 


80 


968.7 


0.02370 


0.06064 


73.9 


118.7 


0.1476 


0.2304 


153.7 


0.2927 


171.7 


0.3220 


82 


993.0 


0.02456 


0.05648 


76.4 


116.6 


0.1578 


0.2195 


153.7 


0.2920 


173.8 


0.3215 


84 


1017.7 


0.02553 


0.05223 


79.4 


113.9 


0.1679 


0.2087 


153.7 


0.2914 


176.0 


0.3209 


86 


1043.0 


0.02686 


0.04789 


83.3 


110.4 


0.1781 


0.1978 


153.7 


0.2907 


178.2 


0.3204 


87.8 


1069.9 


0.03454 


0.03454 


97.0 


97.0 


0.1880 


0.1880 


153.7 


0.2901 


180.1 


0.3199 



CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS 



Aluminum Oxide, (Alumina), in a porous, amorphous form is a solid 
adsorbent frequently called by the common name activated alumina, and 
containing small amounts of hydrated aluminum oxide, and very small 
amounts of soda, and various metallic oxides. A good grade of activated 
alumina will show 92 per cent of AkO z , and its soda content will be com- 
bined with silica and alumina into an insoluble compound. This substance 
also has the property of adsorbing certain gases and certain vapors other 




"80 I2D 160 200" 
ENTERING AIR TEMPERATURE, F 

FIG. 1. TEMPERATURE VAPOR PRESSURE CONCENTRATION RELATION FOR A 
SILICA GEL BED AT CONSTANT TEMPERATURE 

than water vapor a property which is sometimes useful in air condi- 
tioning installations. It is available commercially in granules ranging 
trom a fine powder to pieces approximately 1.5 in. in diameter. It has 
iiigh adsorptive capacity per unit of weight, and is non-toxic. It may be 
repeatedly re-activated after becoming saturated with adsorbed moisture 
without practical loss of its adsorptive ability. In the grade frequently 
US !i o r ^ d T ng e re - activati <>n may be accomplished at temperatures 
under 350 F. Specific gravity is 3.25 and the pores are reported to occupy 
58 per cent of the volume of each particle. For most estimating purposes 

39 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 3. PROPERTIES OF DICHLORODIFLUOROMETHANE(FIO) 



HEAT CONTENT AND ENTROPY TAKEN FROM -40 F 



rlS; ** 

T| SP' LBMB 
h SQ!N. 


VOLUME 
1 Heat Content 


Entropy 


25 F Superheat 


50 F Superheat 


Liquid Vapor Uquid 1 Vapor 


Liquid 


Vapor 


Ht. Ct. 


Entropy 


Ht. Ct. 


Entropy 


i 23.870.0110J 1.637 8.25 


78.21 


0.01869 


0.17091 


81.71 


0.17829 


85.26 


0.18547 


2 24 890.01101 1.5741 8.67 


78.44 


0.01961 


0.17075 


81.94 


0.17812 


85.51 


0.18529 


4 


25.960.0111 1.514 9.10 


i 78.67 


0.02052 


0.17060 


82.17 


0.17795 


85.76 


0.18511 


5 26. 510.0111! 1.485! 9.32 78.79 


0.02097 


0.17052 


82.29 


0.17786 


85.89 


0.18502 


6 ! 27.050.0111 1.457 


9.53 


78.90 


0.02143 


0.17045 


82.41 


0.17778 


86.01 


0.18494 


8 ' 28.180.0111J 1.403 9.96 


79.13 


0.02235 


0.17030 


82.66 


0.17763 


86.26 


0.18477 


10 : 29.350.0112 1.3511 10.39 


79.36 


0.02328 


0.17015 


82.90 


0.17747 


86.51 


0.18460 


12 ; 30.560.0112 1.301 


10.82 


79.59 


0.02419 


0.17001 


83.14 


0.17,733 


86.76 


0.18444 


14 31.800.0112 1.253 


11.26 


79.82 


0.02510 


0.16987 


83.38 


0.17720 


87.01 


0.18429 


16 ! 33.0810. 0112 


1.207 


11.70 


80.05 


0.02601 


0.16974 


83.61 


0.17706 


87.26 


0.18413 


18 j 34.400.01131 1.163 


12.12 


80.27 


0.02692 


0.16961 


83.85 


0.17693 


87.51 


0.18397 


20 35. 75 0.0113| 1.121 


12.55 


80.49 


0.02783 


0.16949 


84.09 


0.17679 


87.76 


0.18382 


22 ! 37.150.0113 1.081 


13.00 


80.72 


0.02873 


0.16938 


84.32 


0.17666 


88.00 


0.18369 


24 38.580.0113 


1.043 


13.44 


80.95 


0.02963 


0.16926 


84.55 


0.17652 


88.24 


0.18355 


26 40.070.0114 


1.007 


13.88 


81.17 


0.03053 


0.16913 


84.79 


0.17639 


88.49 


0.18342 


28 41.590.0114 


0.973 


14.32 


81.39 


0.03143 


0.16900 


85.02 


0.17625 


88.73 


0.18328 


30 


43.160.0115 


0.939 


14.76 


81.61 


0.03233 


0.16887 


85.25 


0.17612 


88.97 


0.18315 


32 


44.77 


0.0115 


0.908 


15.21 


81.83 


0.03323 


0.16876 


85.48 


0.17600 


89.21 


0.18303 


34 


46.420.0115 


0.877 


15.65 


82.05 


0.03413 


0.16865 


85.71 


0.17589 


89.45 


0.18291 


36 48. 13)0.0116 


0.848 


16.10 


82.27 


0.03502 


0.16854 


85.95 


0.17577 


89.68 


0.18280 


38 49.88^0.0116 


0.819 


16.55 


82.49 


0.03591 


0.16843 


86.18 


0.17566 


89.92 


0.18268 


39 50.780.0116 


0.806 


16.77 


82.60 


0.03635 


0.16838 


86-29 


0.17560 


90.04 


0.18262 


40 ; 51.680.0116 


0.792 


17.00 


82.71 


0.03680 


0.16833 


86.41 


0.17554 


90.16 


0.18256 


41 ; 52.70:0.0116 


0.779 


17.23 


82.82 


0.03725 


0.16828 


86.52 


0.17549 


90.28 


0.18251 


42 53.510.0116 


0.767 


17.46 


82.93 


0.03770 


0.16823 


86.64 


0.17544 


90.40 


0.18245 


44 


55.40)0.0117 


0.742 


17.91 


83.15 


0.03859 


0.16813 


86.86 


0.17534 


90.65 


0.18235 


46 


57.35 


0.0117 


0.718 


18.36 


83.36 


0.03948 


0.16803 


87.09 


0.17525 


90.89 


0.18224 


48 


59.35 


0.0117 


0.695 


18.82 


83.57 


0.04037 


0.16794 


87.31 


0.17515 


91.14 


0.18214 


50 


61.390.0118 0.673 


19.27 


83.78 


0.04126 


0.16785 


87.54 


0.17505 


91.38 


0.18203 


52 


63.49 


0.0118 


0.652 


19.72 


83.99 


0.04215 


0.16776 


87.76 


0.17496 


91.61 


0.18193 


54 


65.63jO.0118 


0.632 


20.18 


84.20 


0.04304 


0.16767 


87.98 


0.17486 


91.83 


0.18184 


56 


67.8410. 0119 


0.612 


20.64 


84.41 


0.04392 


0.16758 


88.20 


0.17477 


92.06 


0.18174 


58 


70.100.0119 


0.593 


21.11 


84.62 


0.04480 


0.16749 


88.42 


0.17467 


92.28 


0.18165 


60 72.41jO.0119 


0.575 


21.57 


84.82 


0.04568 


0.16741 


88.64 


0.17458 


92.51 


0.18155 


62 i 74.77 


0.0120 


0.557 


22.03 


85.02 


0.04657 


0.16733 


88.86 


0.17450 


92.74 


0.18147 


fri 


77.20 


0.0120 


0.540 


22.49 


85.22 


0.04745 


0.16725 


89.07 


0.17442 


92.97 


0.18139 


66 79.67 


0.0120 


0.524 


22.95 


85.42 


0.04833 


0.16717 


89.29 


0.17433 


93.20 


0.18130 


68 82.24 


0.0121 


0.508 


23.42 


85.62 


0.04921 


0.16709 


89.50 


0.17425 


93.43 


0.18122 


70 


84.82 


0.0121 


0.493 


23.90 


85.82 


0.05009 


0.16701 


89.72 


0.17417 


93.66 


0.18114 


72 ! 87.50 


0.0121 


0.479 


24.37 


86.02 


0.05097 


0.16693 


89.93 


0.17409 


93.99 


0.18106 


74 90.20 


0.0122 


0.464 


24.84 


86.22 


0.05185 


0.16685 


90.14 


0.17402 


94.12 


0.18098 


76 93.00 


0.0122 


0.451 


25.32 


86.42 


0.05272 


0.16677 


90.36 


0.17394 


94.34 


0.18091 


78 95.85 


0.0123 


0.438 


25.80 


86.61 


0.05359 


0.16669 


90.57 


0.17387 


94.57 


0.18083 


80 98.76 


0.0123 


0.425 


26.28 


86.80 


0.05446 


0.16662 


90.78 


0.17379 


94.80 


0.18075 


82 1101.70 


0.0123 


0.413 


26.76 


86.99 


0.05534 


0.16655 


90.98 


0.17372 


95.01 


0.18068 


84 il04.S 


0.0124 


0.401 


27.24 


87.18 


0.05621 


0.16648 


91.18 


0.17365 


95.22 


0.18061 


86 i!07.9 


0.0124 


0.389 


27.72 


87.37 


0.05708 


0.16640 


91.37 


0.17358 


95.44 


0.18054 


88 


111,1 


0.0124 


0.378 


28.21 


87.56 


0.05795 


0.16632 


91.57 


0.17351 


95.65 


0.18047 


90 


114.3 


0.0125 


0.368 


28.70 


87.74 


0.05882 


0.16624 


91.77 


0.17344 


95.86 


0.18040 


92 


117.7 


0.0125 0.357 


29.19 


87.92 


0.05969 


0.16616 


91.97 


0.17337 


96.07 


0.18033 


94 


121.0 


0.0126 0.347 


29.68 


88.10 


0.06056 


0.16608 


92.16 


0.17330 


96.28 


0.18026 


96 


124.5 


0.0126 


0.338 


30.18 


88.28 


0.06143 


0.16600 


92.36 


0.17322 


96 50 


0.18018 


98 128.0 


0.0126 


0.328 


30.67 


88.45 


0.06230 


0.16592 


92.55 


0.17315 


96.71 


0.18011 


100 J131.6 


0.0127 


0.319 


31.16 


88.62 


0.06316 


0.16584 


92.75 


0.17308 


96.92 


18004 


102 


135.3 


0.0127 


0.310 


31.65 


88.79 


0.06403 


0.16576 


92.93 


0.17301 


97.12 


0.17998 



40 



CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS 



TABLE 3. PROPERTIES OF DICHLORODIFLUOROMETHANE (Fi 2 ) Continued 



SAT. 
TEMP. 
F 


ABS 
PRESS. 
LB PER 
SQ!N. 


VOLUME 


HEAT CONTENT AND ENTROPY TAKEN FBOM 40 F 


Heat Content 


Entropy 


25 F Superheat 


SO F Superheat 


Liquid 


Vapor 


Liquid 


Vapor 


Liquid 


Vapor 


Ht. Ct. 


Entropy 


Ht Ct. 


Entropy 


104 


139.0 


0.0128 


0.302 


32.15 


88.95 


0.06490 


0.16568 


93.11 


0.17294 


97.32 


0.17993 


106 


142.8 


0.0128 


0.293 


32.65 


89.11 


0.06577 


0.16560 


93.30 


0.17288 


97.53 


0.17987 


108 


146.8 


0.0129 


0.285 


33.15 


89.27 


0.06663 


0.16551 


93.48 


0.17281 


97.73 


0.17982 


110 


150.7 


0.0129 


0.277 


33.65 


89.43 


0.06749 


0.16542 


93.66 


0.17274 


97.93 


0.17976 


112 


154.8 


0.0130 


0.269 


34.15 


89.58 


0.06836 


0.16533 


93.82 


0.17266 


98.11 


0.17969 


114 


158.9 


0.0130 


0.262 


34.65 


89.73 


0.06922 


0.16524 


93.98 


0.17258 


98.29 


0.17961 


116 


163.1 


0.0131 


254 


35.15 


89.87 


0.07008 


0.16515 


94.15 


0.17249 


98.4810.17954 


118 


167.4 


0.0131 


0.247 


35.65 


90.01 


0.07094 


0.16505 


94.31 


0.17241 


98.66 


0.17946 


120 


171.8 


0.0132 


0.240 


36.16 


90.15 


0.07180 


0.16495 


94.47 


0.17233 


98.84 


0.17939 


122 


176.2 


0.0132 


0.233 


36.66 


90.28 


0.07266 


0.16484 


94.63 


0.17224 


99.01 


0.17931 


124 


180.8 


0.0133 


0.227 


37.16 


90.40 


0.07352 


0.16473 


94.78 


0.17215 


99.18 


0.17922- 


126 


185.4 


0.0133 


0.220 


37.67 


90.52 


0.07437 


0.16462 


94.94 


0.17206 


99.35 


0.17914 


128 


190.1 


0.0134 


0.214 


38.18 


90.64 


0.07522 


0.16450 


95.09 


0.17196 


99.53 


0.17906 


130 


194.9 


0.0134 


0.208 


38.69 


90.76 


0.07607 


0.16438 


95.25 


0.17186 


99.70 


0.17897 


132 


199.8 


0.0135 


0.202 


39.19 


90.86 


0.07691 


0.16425 


95.41 


0.17176 


99.87 


0.17889 


134 


204.8 


0.0135 


0.196 


39.70 


90.96 


0.07775 


0.16411 


95.56 


0.17166 


100.04 


0.17881 


136 


209.9 


0.0136 


0.191 


40.21 


91.06 


0.07858 


0.16396 


95.72 


0.17156 


100.22 


0.17873 


138 


215.0 


0.0137 


0.185 


40.72 


91.15 


0.07941 


0.16380 


95.87 


0.17145 


100.39 


0.17864 


140 


220.2 


0.0138 


0.180 


41.24 


91.24 


0.08024 


0.16363 


96.03 


0.17134 


100.56 


0.17856 



the volume-weight relation on a dry basis may be taken as 50 Ib per cubic 
foot although in the smaller sizes the packed weight may be as much as 
64 Ib per cubic foot. 

Silicon Dioxide, (Silica), in a special form obtained by suitably mixing 
sulphuric acid with sodium silicate, is another solid adsorbent and is 
commonly called silica gel. Its capillary structure is exceedingly small, 
so small that its exact structure has to be deduced rather than observed. 
The gel is available commercially in a wide variety of sizes of granules 
ranging from 4 to 300 mesh. It has high adsorptive capacity per unit 
of weight and is non-toxic, may be repeatedly re-activated without 
practical deterioration. Re-activation may be accomplished at tem- 
peratures of air up to 600 F although it is frequently accomplished with 
air or other gases at temperatures not over 350 F. Volume of the capillary 
pores is reported to be from 50 to 70 per cent of the total solid volume. 
For most estimating purposes the volume-weight relation can be assumed 
as from 38 to 40 Ib per cubic foot on a dry basis. 

Other substances having properties which make them available as 
solid adsorbents include lamisilate and charcoal but details of their 
physical properties are not available. 

Nature of Adsorption Process 

Adsorption is accomplished without chemical change between the air 
and the adsorbent substance. The adsorbent does not go into solution but 
water vapor is extracted from the air-vapor stream passing through the 
bed of adsorbent material and is caught and retained in the capillary 
pores. The exact nature of the process which goes on during adsorption 

41 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 4. PROPERTIES OF METHYL CHLORIDE 



HEAT CONTEST AND ENTROPY TAKEN FROM -40 F 



F SslN? 

I 


VoL-nos 
I Heat Content ' Entropy 


100 F Superheat 


200 F Superheat 


Liquid ;' Vapor Liquid Vapor 


Liquid 


Vapor 


Ht. Ct. 


Entropy 


Ht. Ct. 


Entropy 


18.73 0.0162 : 5.052 14,4 192.4 


0.0328 


0.4197 


215.6 


0.467 


237.2 


0.507 


2 19.60 0.0162 4.856 15.1 i 193.1 


0.0344 


0.4196 


216.2 


0.466 


237.7 


0.505 


4 I 20.47 0.0163 , 4.661 15.8 


193.80.0360 


0.4195 


216.7 


0.465 


238.2 


0.504 


5 i 20.91:0.0163 


4.563 16.2 


194.1 


0.0368 


0.4195 


217.0 


0.464 


238.5 


0.503 


6 


21. 39 ; 0.0163 4.476 16.6 


194.4 


0.0376 


0.4194 


217.3 


0.464 


238.8 


0.502 


8 


22. 34' 0.0164 


4.303 17.3 


195.1 


0.0391 


0.4193 


217.9 


0.463 


239.4 


0.501 


10 


23.30 0.0164 


4.129 18.1 


195.8 


0.0407 


0.4192 


218.5 


0.463 


240.0 


0.500 


12 


24.38 0.0164 ' 3.984 18.8 


196.3 


0.0423 


0.4184 


219.0 


0.462 


240.5 


0.499 


14 


25.46 0.0164 3.839 19.6 


196.7 


0.0439 


0.4176 


219.5 


0.462 


241.0 


0.498 


16 


26.55 0,0165 3.693 


20.3 


197.2 


0.0454 


0.4168 


220.0 


0.461 


241.5 


0.498 


18 


27. 63' 0.0165 


3.548 


21.1 


197.6 


0.0472 


0.4160 


220.5 


0.461 


242.0 


0.497 


20 


28. 71 ! 0.0166 


3.403 


21.8 


198.1 


0.0486 


0.4152 


221.0 


0.460 


242.5 


0.496 


22 


29.98 0.0166 


3.288 


22.5 


198.5 


0.0501 


0.4148 


221.5 


0.459 


243.0 


0.495 


24 


31.25 0.0166 


3.172 


23.3 


198.9 


0.0516 


0.4143 


222.0 


0.459 


243.6 


0.495 


26 


32.53 0.0167 


3.057 


24.0 


199.3 


0.0532 


0.4139 


222.4 


0.458 


244.1 


0.494 


28 


33. 801 0.0167 


2.941 


24.8 


199.7 


0.0547 


0.4134 


222.9 


0.458 


244.7 


0.494 


30 


35. 0/1 0.0168 


2.826 


25.5 


200.1 


0.0562 


0.4130 


223.4 


0.457 


245.2 


0.493 


32 36.55 


0.0168 


2.734 


26.2 


200.5 


0.0577 


0.4124 


223.9 


0.456 


245.7 


0.492 


34 


38.03 0.0169 


2.642 


27.0 


200.9 


0.0592 


0.4118 


224.3 


0.455 


246.2 


0.492 


36 


39.5110.0169 


2.549 


27.7 


201.4 


0.0607 


0.4111 


224.8 


0.455 


246.7 


0.491 


38 


40.99 


0.0169 


2.457 


28.5 


201.8 


0.0622 


0.4105 


225.2 


0.454 


247.2 


0.491 


39 


41.73 


0.0170 


2.411 


28.8 


202.0 


0.0629 


0.4102 


225.5 


0.453 


247.4 


0.490 


40 


42.47 


0.0170 


2.365 


29.2 


202.2 


0.0637 


0.4099 


225.7 


0.453 


247.7 


0.490 


41 


43.33 


0.0170 


2.328 


29.6 


202.4 


0.0644 


0.4096 


225.9 


0.453 


248.0 


0.490 


42 


44.18 


0.0171 


2.290 


29.9 


202.6 


0.0651 


0.4093 


226.1 


0.452 


248.3 


0.489 


44 


45.89 


0.0171 


2.216 


30.7 


203.0 


0.0666 


0.4087 


226.6 


0.451 


248.8 


0.489 


46 


47.61 


0.0171 


2.141 


31.4 


203.3 


0.0680 


0.4081 


227.0 


0.451 


249.4 


0.488 


48 


49.32 


0.0172 


2.067 


32.2 


203.7 


0.0695 


0.4075 


227.5 


0.450 


249.9 


0.488 


50 


51.03 


0.0172 


1.992 


32.9 


204.1 


0.0709 


0.4069 


227.9 


0.449 


250.5 


0.487 


52 


53.00 


0.0172 


1.931 


33.7 


204.4 


0.0724 


0.4063 


228.2 


0.448 


251.0 


0.486 


54 


54.97 


0.0173 


1.870 


34.4 


204.7 


0.0739 


0.4056 


228.6 


0.448 


251.5 


0.486 


56 


56.94 


0.0173 


1.810 


35.2 


205.1 


0.0754 


0.4050 


228.9 


0.447 


252.0 


0.485 


58 


58.91 


0.0173 


1.749 


35.9 


205.4 


0.0769 


0.4043 


229.3 


0.447 


252.5 


0.485 


60 


60.88 


0.0174 


1.688 


36.7 


205.7 


0.0784 


0.4037 


229.6 


0.446 


253.0 


0.484 


62 


63.13 


0.0174 


1.638 


37.4 


206.0 


0.0798 


0.4030 


229.9 


0.445 


253.5 


0.483 


64 


65.37 


0.0174 


1.588 


38.2 


206.3 


0.0812 


0.4024 


230.3 


0.444 


254.0 


0.483 


66 


67.62 


0.0175 


1.539 


38.9 


206.6 


0.0827 


0.4017 


230.6 


0.443 


254.5 


0.482 


68 


69.86 


0.0175 


1.489 


39.7 


206.9 


0.0841 


0.4011 


231.0 


0.442 


255.0 


0.482 


70 


72.11 


0.0176 


1.439 


40.4 


207.2 


0.0855 


0.4004 


231.3 


0.441 


255.5 


0.481 


72 


74.66 


0.0176 


1.398 


41.1 


207.5 


0.0869 


0.3998 


231.6 


0.440 


256.0 


0.480 


74 


77.21 


0.0177 


1.357 


41.9 


207.7 


0.0883 


0.3992 


232.0 


0.439 


256,5 


0.480 


76 


79.76 


0.0177 


1.315 


42.6 


208.0 


0.0898 


0.3985 


232.3 


0.439 


256.9 


0.479 


78 


82.31 


0.0178 


1.274 


43.4 


208.2 


0.0912 


0.3979 


232.7 


0.438 


257.4 


0.479 


80 


84.86 


0.0178 


1.233 


44.1 


208.5 


0.0926 


0.3973 


233.0 


0.437 


257.9 


0.478 


82 


87.74 


0.0178 


1.199 


44.8 


208.7 


0.0940 


0.3967 


233.3 


0.436 


258.4 


0.478 


84 


90.62 


0.0179 


1.165 


45.6 


209.0 


0.0953 


0.3960 


233.6 


0.435 


258.9 


0.477 


86 


93.50 


0.0179 


1.130 


46.3 


209.2 


0.0967 


0.3954 


233.9 


0.435 


259.4 


0.477 


88 


96.38 


0.0180 


1.096 


47.1 


209.5 


0.0980 


0.3947 


234.2 


0.434 


259.9 


0.476 


90 


99.26 


0.0180 


1.062 


47.8 


209.7 


0.0994 


0.3941 


234.5 


0.433 


260.4 


0.476 


92 


102.49 


0.0180 


1.033 


48.6 


209.9 


0.1008 


0.3935 


234.8 


0.433 


260.8 


0.476 


94 


105.72 


0.0181 


1.005 


49.3 


210.2 


0.1022 


0.3929 


235.1 


0.432 


261.2 


0.475 


96 


108.94 


0.0181 


0.9764 


50.1 


210.4 


0.1035 


0.3922 


235.4 


0.432 


261.6 


0.475 


98 


112.17 


0.0182 


0.9478 


50.8 


210.7 


0.1049 


0.3916 


235.7 


0.431 


262 


0.474 


100 


115.40 


0.0182 


0.9193 


51.6 


210.9 


0.1063 


0.3910 


236.0 


0.431 


262.4 


0^474 


102 


119.00 


0.0183 


0.8952 


52.3 


211.1 


0.1076 


0.3903 


236.4 


0.430 


262.8 


0.474 



42 



CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS 



TABLE 4. PROPERTIES OF METHYL CHLORIDE (Continued) 









HEAT CONTENT AND ENTBOPY TAKES FBOJI 40 F 


O.m 


ABS 


VOTTTMTS 




TEMP. 
F 


PRESS. 
LB PER 
SQ IN. 




Heat Content 


Entropy 


100 F Superheat 


200 F Superheat 






Liquid 


Vapor 


Liquid 


Vapor 


Liquid 


Vapor 


Ht. Ct. 


Entropy 


HtCt 


Entropy 


104 


122.60 


0.0183 


0.8712 


53.1 


211.3 


0.1090 


0.3897 


236.8 


0.430 


263.2 


0.473 


106 


126.20 


0.0184 


0.8471 


53.8 


211.4 


0.1103 


0.3890 


237.1 


0.429 


263.5 


0.473 


108 


129.80 


0.0184 


0.8231 


54.6 


211.6 


0.1117 


0.3884 


237.5 


0.429 


263.9 


0.472 


110 


133.40 


0.0185 


0.7990 


55.3 


211.8 


0.1130 


0.3877 


237.9 


0.428 


264.3 


0.472 


112 


137.42 


0.0185 


0.7786 


56.1 


212.0 


0.1144 


0.3871 


238.1 


0.427 


264.6 


0.471 


114 


141.44 


0.0185 


0.7583 


56.8 


212.2 


0.1157 


0.3864 


238.3 


0.427 


264.8 


0.470 


116 


145.46 


0.0186 


0.7379 


57.6 


212.4 


0.1171 


0.3858 


238.6 


0.426 


265.1 


0.470 


118 


149.48 


0.0186 


0.7176 


58.3 


212.6 


0.1184 


0.3851 


238.8 


0.426 


265.3 


0.469 


120 


153.50 


0.0187 


0.6972 


59.1 


212.8 


0.1198 


0.3845 


239.0 


0.425 


265.6 


0.468 



is not known but it is stated that the action is brought about by surface 
condensation, and also by a difference between the vapor pressure of the 
water condensing inside the pores and the partial pressure of the water 
vapor in the air-vapor mixture. The adsorbing process in the bed can 
continue until the vapor pressures come into equilibrium. The amount 
of vapor adsorbed will depend on the adsorbent substances being used 
but for any single substance the amount depends on the temperature of 
the bed as well as on the partial pressure of the air-vapor mixture being 
passed over it. 

As the process of adsorption goes on heat is liberated in the bed. The 
heat so liberated is the latent heat of the water vapor condensed together 
with the so-called heat of wetting. For a pound of water vapor at 60 F 
the latent heat released by condensation is approximately 1057 Btu. 
The heat of wetting for silica gel, for example, is about 200 Btu, making a 
total heat of adsorption of approximately 1257 Btu per pound of water 
adsorbed from the air-vapor mixture passing through the silica gel bed. 
The heat of wetting varies with the substance being used as the adsorbent 
while the latent heat of condensation depends only on the temperature 
and pressure of the water vapor. 

Temperature-Pressure-Concentration Relations 

Since the adsorptive ability of an adsorbent depends on the temperature 
of the bed and on the partial pressure difference between the pores and the 
air-vapor mixture it is important to know the pressures and temperatures 
at which pressure equilibrium is reached. 

Evidently the equilibrium conditions represent the limits beyond 
which adsorption of vapor cannot continue. The relationship can be 
shown graphically and Fig. 1 is such a chart for silica gel. Charts of like 
nature can be plotted for other adsorbent materials. 

Fig, 1 shows the equilibrium conditions for a gel bed maintained at 
constant temperature while the water vapor adsorption is allowed to 
continue until pressure equilibrium is reached. Each curve on the chart 
show a certain dew-point temperature, and therefore a certain pressure, 
of the saturated water vapor. 

43 



HEATING VENTILATING . AIR CONDITIONING GUIDE 1938 



TABLE 5. PROPERTIES OF MONOFLUOROTRICHLOROMETHANE (Fn) 



SAT. 
Tin*. 
F 


ABS 
PRKS. 
LB PIE 
Sal*. 


i VOLUME 


MTCAT UONCTNT AND .ttNTBOPY TAKEN i? BOM 40 JB 


i Heat Content 


Entropy 


25 F Superheat 


SO F Superheat 


; Liquid j Vapor ! Liquid Vapor 


Liquid 


Vapor 


Ht. Ct. 


Entropy 


Ht. Ct. 


Entropy 





2. 59J 0.01020! 13. 700 


7.81 


90.4 


0.0178 


0.1975 


93.9 


0.2049 


97.4 


0.2120 


5 ; 2.9610.01024S12.100 


8.81 


91.2 


0.0200 


0.1974 


94.7 


0.2047 


98.2 


0.2117 


10 : 3. 38 i 0.01028! 10.700 


9.82 


92.0 


0.0222 


0.1973 


95.5 


0.2045 


99.0 


0.2114 


15 


3.85 


0.010321 9.530 


10.80 


92.8 


0.0243 


0.1971 


96.3 


0.2043 


99.8 


0.2111 


20 


4.3610.01036! 8.490 


11.90 


93.7 


0.0264 


0.1970 


97.2 


0.2041 


100.7 


0.2109 


25 


4.94 


0.01040 


7.580 


12.90 


94.5 


0.0286 


0.1969 


98.0 


0.2039 


101.5 


0.2107 


30 


5.57 


0.01045 


6.770 


13.90 


95.3 


0.0307 


0.1969 


98.8 


0.2038 


102.3 


0.2105 


35 6.2710.01049 


6.080 


14.90 


96.1 


0.0328 


0.1968 


99.6 


0.2037 


103.1 


0.2103 


40 


7.03 0.01053 


5.460 


16.00 


96.8 


0.0349 


0.1968 


100.3 


0.2036 


103.8 


0.2101 


45 


7.88 


0.01057 


4.920 


17,00 


97.6 


0.0370 


0.1967 


101.1 


0.2035 


104.6 


0.2099 


50 


8.79 


0.01062 


4.440 


18.10 


98.4 


0.0391 


0.1967 


101.9 


0.2034 


105.4 


0.2098 


55 


9.80 


0.01066 


4.020 


19.10 


99.2 


0.0412 


0.1967 


102.7 


0.2033 


106.2 


0.2097 


60 


10.90 


0.01071 


3.640 


20.20 


100.0 


0.0432 


0.1967 


103.5 


0.2033 


107.0 


0.2096 


65 


12.10 


0.01076 


3.300 


21.30 


100.8 


0.0453 


0.1967 


104.3 


0.2032 


107.8 


0.2094 


70 


13.40 


0.01081 


3.000 


22.40 


101.5 


0.0473 


0.1967 


105.0 


0.2032 


108.5 


0.2093 


75 


14.80 


0.01086 


2.740 


23.50 


102.2 


0.0493 


0.1967 


105.7 


0.2031 


109.2 


0.2092 


80 


16.30 


0.01091 


2.500 


24.50 


102.9 


0.0513 


0.1966 


106.4 


0.2030 


109.9 


0.2090 


85 


17.90 


0.01096 


2.280 


25.60 


103.6 


0.0533 


0.1966 


107.1 


0.2029 


110.6 


0.2089 


90 


19.70 


0.01101 


2.090 


26.70 


104.4 


0.0553 


0.1966 


107.9 


0.2028 


111.4 


0.2088 


95 


21.60 


0.01106 


1.918 


27.80 


105.1 


0.0573 


0.1966 


108.6 


0.2028 


112.1 


0.2087 


100 


23.60 


0.01111 


1.761 


28.90 


105.7 


0.0593 


0.1965 


109.2 


0.2027 


112.7 


0.2085 


105 


25.90 


0.01116 


1.620 


30.10 


106.4 


0.0613 


0.1965 


109.9 


0.2026 


113.4 


0.2084 



As an example in the interpretation of the chart consider the case when 
moist air at a temperature of 80 F and a partial vapor pressure of 0.5 in 
of mercury flows through a bed of silica gel which is at a temperature of 
80 F. The chart indicates that the equilibrium of pressure between the 
air-vapor mixture and the bed is reached when the dry bed has adsorbed 
moisture to the extent of 31 per cent of the weight when dry. When this 
happens the bed can adsorb no more moisture unless its temperature 
is changed. 

In practice however the adsorbent bed is seldom held at a steady tem- 
perature in air conditioning applications and neither is the adsorption 
process permitted to continue until moisture equilibrium is reached 
Instead, the^bed temperature varies and the bed is re-activated before 
equilibrium is approached. While charts of this kind can show the 
limiting properties of the substances they are seldom directly applicable 
to the solution of air conditioning problems unless considerable additional 
information is available. This takes the form of performance data cover- 
ing the characteristics of the equipment in which the adsorbent bed is 
placed. Such performance data are beyond the scope of this chapter. 

Liquid Absorbents 

Any absorbent substance may be used as an air drying agent if it has a 

JS^wCTSf loW *V han . the 7 a P r P^re in the i-vapor mixture 
from which the moisture is to be removed. Absorbents are character- 
istically water solutions of materials in which the vapor pressure is 

44 



CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS 



reduced to a suitable level by governing the concentration of the solution. 
In addition to haying a suitable low vapor pressure, a practical absorbent 
must also be widely available at economical cost, be non-corrosive, 
odorless, non-toxic, chemically inert against any impurities in the air 
stream, stable over the range of use and especially it must not precipitate 
out at the lowest temperature to which the apparatus is exposed. It must 
have low viscosity and be capable of being economically regenerated or 
concentrated after having been diluted by absorbing moisture. 

Water solutions, or brines, of the chlorides of various inorganic elements 
such as calcium chloride and lithium chloride are the absorbents most 
frequently used in connection with air conditioning applications and de- 
tailed attention is confined to these two in this chapter. 

Nature of Absorption Process 

The application consists of bringing the air-vapor stream into intimate 
contact with the absorbent, permissably by passing the air stream through 
a finely divided spray of the brine but more generally by passing the air 
over a metal surface coil where the liquid absorbent presents a large 
surface to the air stream. The difference in vapor pressures causes some 
of the vapor in the air-vapor mixture to migrate into the brine. Here it 
condenses into liquid water and decreases the concentration of the absor- 
bent. In order that the process be continuous means must be provided 
for counteracting the diluting effect of the extracted moisture and also for 
maintaining the temperature of the brine sufficiently low to hold the 
desired vapor pressure. 

As the water vapor is added to the absorbent and condenses, it gives up 
its latent heat of condensation which tends to raise the temperature of 
both the absorbent and the moist air stream. For every pound of water 
absorbed and condensed the heat added to the air stream and the brine 

TABLE 6. PROPERTIES OF WATER 



SAT. 
TEMP. 
F 


ABS 
PRESS. 
LB PER 
3d IN. 


VOLUME 


HEAT CONTENT AND ENTROPY TAKEN FBOM -1-32 F 


Heat Content 


Entropy 


50 F Superheat 


100 F Superheat 


Liquid 


Vapor 


Liquid 


Vapor 


Liquid 


Vapor 


HtCt. 


Entropy 


HtOL 


Entropy 


32 


0.0887 


0.01602 


3296.0 


0.00 


1073.0 


0.0000 


2.1826 


1096.9 


2.2277 


1120.8 


2.2688 


35 


0.1000 


0.01602 


2941.0 


3.02 


1074.4 


0.0062 


2.1724 


1098.3 


2.2172 


1122.2 


2.2581 


40 


0.1217 


0.01602 


2441.0 


8.05 


1076.8 


0.0163 


2.1555 


1100.6 


2.2000 


1124.5 


2.2406 


45 


0.1475 


0.01602 


2034.0 


13.07 


1079.2 


0.0262 


2.1390 


1102.9 


2.1832 


1126.7 


2.2234 


50 


0.1780 


0.01602 


1702.0 


18.08 


1081.5 


0.0361 


2.1230 


1105.2 


2.1667 


1129.0 


2.2066 


55 


0.2140 


0.01603 


1430.0 


23.08 


1083.9 


0.0459 


2.1073 


1107.5 


2.1506 


1131.3 


2.1902 


60 


0.2561 


0.01603 


1206.0 


28.08 


1086.2 


0.0556 


2.0920 


1109.8 


2.1349 


1133.5 


2.1742 


65 


0.3054 


0.01604 


1021.0 


33.08 


1088.6 


0.0652 


2.0771 


1112.2 


2.1196 


1135.8 


2.1585 


70 


0.3628 


0.01605 


868.0 


38.07 


1090.9 


0.0746 


2.0625 


1114.5 


2.1046 


1138.1 


2.1432 


75 


0.4295 


0.01606 


740.0 


43.06 


1093.2 


0.0840 


2.0483 


1116.7 


2.0900 


1140.3 


2.1283 


80 


0.507 


0.01607 


632.9 


48.05 


1095.5 


0.0933 


2.0344 


1119.0 


2.0758 


1142.5 


2.1138 


85 


0.596 


0.01609 


543.3 


53.04 


1097.8 


0.1025 


2.0208 


1121.2 


2.0619 


1144.7 


2.0996 


90 


0.698 


0.01610 


467.9 


58.03 


1100.0 


0.1116 


2.0075 


1123.4 


2.0483 


1146.8 


2.0857 


95 


0.815 


0.01612 


404.2 


63.01 


1102.3 


0.1206 


1.9946 


1125.6 


2.0350 


1148.9 


2.0721 


100 


0.949 


0.01613 


350.3 


68.00 


1104.6 


0.1296 


1.9819 


1127.9 


2.0220 


1151.1 


2.0588 


105 


1.101 


0.01615 


304.4 


72.98 


1106.8 


0.1384 


1.9695 


1130.2 


2.0093 


1153.2 


2.0458 



For properties of steam at high temperatures, see Page 28. 

45 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 7. DEW-POINT OF AIR IN EQUILIBRIUM WITH LITHIUM CHLORIDE SOLUTIONS 
CONCENTRATION* IN GRAM MOLS OF LITHIUM CHLORIDE PER 1000 GRAINS WATER 



o.o 2.0 , 4.0 6.0 



5.0 



10.0 



12.0 14.0 16.0 , 18.0 ! 20.0 ! 22.0 j 24.0 ! 26.0 J 28.0 , 30.0 



320315.2308,7 


299.9 


290.2 


279.7 


269.4 


259.6251.5244.1236.5,230.0223.8218.6214.5210.3 


300295.4289.1 


280.5 


270.9 


260.6 


250.5 


240.8232.6225.4218.0211.8i205.8200.8196.9,192.8 


280 ; 275.6269.5261.1 


251.7 


241.5 


231.6 


222.2 214.0206.7,199.7 193.5187.8 183.2179.3)175.2 


260255.8250.0241.9 


232.6 


222.7 


212.8 


203.5 195.5188.4 181.7:175.41170.0 165.6'162.0 158.4 


240236.0230.4222.5 


213.5 


203.8 


194.2 


185.0177.1 170.0,163.6157.5'152.2 1 148.3 144.6140.5 


220216.2210.8203.2 


194.4 


184.9 


175.5 


166.4 158.6 151 .6 145.3139.6 134.6,130.7 127.3124.2 


200196.41191-2 


183.9 


175.4 


166.1 


156.7 


148.0 140.3 133.5,127.3;121.9!117.0113.3 110.1 


180 176.6 ; 171.6 164.7 


146.4 


147.3 


138.1 


129.6 122.1;115.5 109.4 104.2| 99.6 96.0, i 


160:156.8,152.1 


;i45.4 


137.4 


128.6 


119.7 


111.3103.9, 97.4 91.61 86.61 82.2 1 




140137.0132.6 


126.1 


118.4 


109.9 


101.3 


93.1 


85.9, 79.5 73.8| 69.0' ; 




120J117.2 113.0 106.8 


99.4 


91.1 


82.7 


74.71 67.8; 61.5! 56.0: ' ; [ 


110107.3il03.2l 97.2 


89.9 


81.9 


73.5 


65.6: 58.8 52.6| 47.1| ! 


100 


97.4 


93.4 


87.5 


80.5 


72.7 


64,4 


56.6: 49.8 43.7i 38.2! ! 


90 


87.5 


83.6 


77.9 


71.0 


63.3 


54.2, 


47.6 1 40.8 34.8;' 29.3' ' 


| 


80 


77.6 


73.8 


68.4 


61.6 


54.0 


46.1 


38.5: 31.8 ! 25,9: 20.6 


i 


70 67.7 


64.0 


58.7 


52.2 


44.8 


37.0 


29.5 


22.91 17.2, 12.0 




60| 57.8 


54.3 


49.1 


42.7 


35.5 


27.9 


20.5 


14.0; 83 


' 


40 


38.0 


34.7 


29.9 


23.9 


16.9 


9.6 


2.4'-3.9! i 




20 




15.1 


10.7 


5.0 


-1.7; 


-8.7 


-15.4! ; 1 : ; ' j 







-4.5 


-8.6 


-13.9 


-20.2 


-27.0 


-33.3 


|!l;! 


; 


















1 1 1 


1 



combined is obtainable from steam tables. For instance, at 60 F the 
amount of this heat is about 1057 Btu. In addition to this heat there is 
involved also the so-called heat of mixing which is frequently considerable. 

Temperature-Pressure-Concentration Relations 

Since the absorption process can continue only as long as there is a 
difference in vapor pressure between the absorbent and the air-vapor 
mixture and since at a given temperature of the absorbent the vapor 
pressure depends on the concentration of the solution, evidently there 

TABLE 8. DENSITY OF LITHIUM CHLORIDE SOLUTIONS 



CONCENTRATION 

MoLSLiCJPKB 

1000 GRAINS 
WATER 


TEMPERATURE DEQ F 





50 


100 


150 


200 


250 


300 



















2 




1.045 


1.037 


1.026 


1.012 






4 


1.090 


1.085 


1.076 


1.064 


1.052 






6 


1.124 


1.119 


1.111 


1.100 


1.087 






8 


1.156 


1.150 


1.143 


1.132 


1.122 






10 


1,188 


1.181 


1.172 


1.162 


1.152 


1.142 




12 


1,217 


1.209 


1.199 


1.188 


1.178 


1.168 




14 


1.242 


1.235 


1.225 


1.214 


1.203 


1.192 




16 




1.257 


1.248 


1.236 


1.226 


1.215 




18 




1.279 


1.270 


1.259 


1.248 


1.237 




20 






1.291 


1.280 


1.279 


1.568 




22 








1.310 


1.289 


1.278 


1.267 


24 








1.317 


1.307 


1.296 


1.286 


26 










1.313 


1.312 


1.302 


28 










1.338 


1.327 


1.318 


30 












1.34 


1.33 


32 














1.35 



46 



CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS 



TABLE 9. VISCOSITY OF LITHIUM CHLORIDE SOLUTIONS (MILLIPOISE) 



TEMP. 
DEGF 


CONCENTRATION IN JM.OLAL 





2 


4 


6 


8 


10 


12 


14 


16 


18 


20 


22 


24 









56.75 


72.44 


97.05 


136.8 


199.5 














20 




28.91 


37.07 


47.42 


63.09 


84.94 


123.3 


178.6 












40 


15.45 


19.91 


25.53 


32.58 


43.05 


58.48 


81.10 


116.1 


165.6 










60 


11.02 


14.26 


18.37 


23.55 


30.90 


41.40 


56.62 


79.80 


111.2 


156.3 








80 


8.61 


11.19 


14.42 


18.62 


24.32 


32.28 


43.45 


60.26 


82.04 


113.8 








100 


6.82 


8.89 


11.48 


14.94 


19.36 


25.59 


33.96 


46.13 


61.52 


84.72 


118.3 






120 


5.60 


7.31 


9.51 


12.30 


15.92 


20.99 


27.67 


36.64 


48.31 


65.77 


89.95 






140 


4.70 


6.15 


8.07 


10.42 


13.43 


17.66 


22.96 


30.06 


38.99 


52.48 


71.12 


95.94 




160 


4.01 


5.25 


6.92 


8.93 


11.51 


15.00 


19.36 


25.06 


32.14 


42.76 


56.89 


75.86 


106.2 


180 


3.48 


4.56 


6.01 


7.78 


10.00 


12.91 


16.56 


21.28 


27.10 


35.48 


46.45 


60.67 


84.33 


200 


3.05 


4.01 


5.28 


6.86 


8.79 


11.22 


14.32 


18.28 


23.12 


29.92 


38.55 


50.70 


67.92 


220 


2.72 


3.58 


4.72 


6.14 


7.83 


9.93 


12.59 


16.00 


20.14 


25.64 


32.96 


43.05 


56.49 


240 


2.43 


3.21 


4.25 


5.50 


7.02 


8.83 


11.12 


14.09 


17.62 


22.18 


28.31 


36.98 


47.42 


260 


2.19 


2.90 


3.84 


4.94 


6.46 


7.91 


9.91 


12.47 


15.50 


19.36 


24.60 


31.92 


40.55 


280 


2.00 


2.66 


3.52 


4.51 


5.75 


7.19 


8.97 


11.27 


14.00 


17.22 


21.78 


28.05 


35.56 


300 


1.86 


2.48 


3.28 


4.17 


5.32 


6.67 


8.28 


10.38 


12.82 


15.70 


19.68 


25.12 


31.92 


320 


1.74 


2.32 


3.08 


3.89 


4.94 


6.19 


7.73 


9.64 


11.86 


14.45 


18.03 


22.80 


29.11 



must be a relation between these quantities which if known would state 
the limits of the process. The relationship would also depend on the 
absorbent being used, and would have to be determined for each substance 
used as an absorbent. Fig. 2 shows this relationship graphically for 
lithium chloride. It will be noted that this chart is essentially similar 
to that shown in Fig. 1 and its direct usefulness is limited by much the 
same considerations. 

In order to permit numerical calculations of air conditioning problems 
it is desirable to have tables for use instead of a chart like Fig. 2, and 
Tables 7, 8, 9 and 10 can be used in making calculations for lithium 
chloride. 

TABLE 10. PROPERTIES OF LITHIUM CHLORIDE SOLUTIONS 



CONCENTRATION 
MOLS (42.4 GRAMS 
LiCZ PER 1000 
GRAINS WATER) 


PARTIAL HEAT 
OP MIXING AT 
F BTU PER LB 


TEMPERATURE COUP. 
OP PARTIAL HEAT 
OP MIXING BTTJ PER 

LB PER F 


SPECIFIC 
HEAT AT 
70 F 


BOILING POINT 
F 
(AT 760 MM 
EG) 


FREEZING 
POINT 


SUBSTANCE THAT 
FIRST SEPARATES 
Our ON 

FREEZING 





0.0 


0.0 


0.998 


212.0 


32 


Ice 


2 


2.04 


-0.014 


0.901 


215.8 


16.3 


Ice 


4 


7.24 


-0.036 


0.831 


221.5 


-5.8 


Ice 


6 


16.7 


-0.069 


0.778 


228.9 


-34.2 


Ice 


8 


31.9 


-0.109 


0.739 


238.1 


-69 


Ice 


10 


51.1 


-0.143 


0.710 


248.4 


-90 


Ice 


12 


75.7 


-0.160 


0.687 


258.8 


-40 


IAC13H& 


14 


90.8 


-0.167 


0.666 


268.9 


1 


LiCl-3HiO 


16 


124.8 


-0.176 


0.647 


277.9 


36.5 


LiCl-2H,0 


18 


145 


-0.186 


0.631 


285.8 


58.1 


LiCl-2H z O 


20 


162 


-0.194 


0.617 


293.2 


86.4 


LiCl-HzO 


22 


171 


-0.20 


0.604 


300.2 


133 


LiCl-HzO 


24 


177 


-0.20 


0.59 


307 


156 


UCl-HiO 


26 


182 


-0.21 


0.58 


313 


180 


LiCLHlO 


28 


191 


-0.21 


0.575 


318 


190 


LiCl-HzO 


30 


194 


-0.21 


0.57 


323 


195 


UClr-H> 


32 


198 


-0.22 


0.56 


328 


280 


LiCl . 



47 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Instead of tabulating the vapor pressure of the solution of lithium 

chloride it ?s SefaSSto tabulate the dew-point of air m equilibrium 

Sth lithium Sloridc, since it is easy to interpolate between values of 

the dew t and not so easy to interpolate accurately between values of 

apo pSre The valuesfor dew-point may be converted to vapor 



CONCENTRATION, PER CENT 
30 40 50 



1000 



500- 



M1XTURE5 OF 
SOLUTION AND LiCI-H 2 O 



MIXTURES OF SOLUTION AND 
LiCl -2H 2 



MIXTURES OF SOLUTION AND 
LiCI-3H 2 




0.1 



FIG. 



10 15 20 25 

CONCENTRATION, MOLAL 

2. TEMPERATURE PRESSURE CONCENTRATIONS FOR LITHIUM CHLORIDE 



pressures, relative humidity, and wet-bulb of air in equilibrium by means 
of the usual psychrometric chart or formula. 

In Tables 7, 8, 9 and 10 the unit of concentration is the mol A 'M' 
molal solution is denned as a solution containing M X 42.37 grains of 
anhydrous lithium chloride per 1000 grains of water. The formula con- 
necting concentration in mols with weight in per cent is equivalent to: 
[100 X M X 42.37] -r [1000 + (M X 42.37)]. 

48 



CHAPTER 2. REFRIGERANTS AND AIR DRYING AGENTS 



PROBLEMS IN PRACTICE 

1 What is the heat content above 40 F of 2.5 Ib of ammonia when under a 
pressure of 92.9 Ih per square inch gage and a temperature of 160 F? 

First determine the condition of the ammonia at the stated temperature and pressure. 
Do this by finding the absolute pressure which in this case is 92.9 Ib gage plus 14.7 or 
107.6 Ib per square inch absolute. From Table 1 note that the saturation temperature 
at this pressure is 60 F. Therefore, the ammonia is superheated 100 F, and the total heat 
per pound can be read directly from the Table as 689.9 Btu. In the 2.5 Ib of ammonia 
there are 2.5 X 689.9, or 1724.75 Btu. 

2 "What volume is necessary to accommodate 0.27 Ib of saturated Fi2 vapor 
when compressed to 99.6 Ib gage? 

The absolute pressure is 99.6 plus 14.7 or 114.3 Ib. In Table 3 find that one pound of 
Fi2 vapor saturated occupies 0.368 cu ft. Then the 0.27 Ib would occupy 0.27 X 0.368, 
or 0.099 cu ft. 

3 How much heat would be removed from air passing over a coil through 
which 2 Ib of methyl chloride per minute is forced? The coil is under a gage 
pressure of 64 Ib per square inch and the liquid refrigerant is completely vapor- 
ized in passing through the coil. 

Find that the absolute pressure is 64 plus 14.7 or 78.7 Ib per sq in. From Table 4 note 
that the saturation temperature at this pressure is 75 F (nearly) and that the heat 
content per pound of the vapor is 207.8 Btu. Also that the heat content of the liquid is 
42.2 Btu per pound. Subtract 42.2 from 207.8 and 165.6 Btu per pound is the heat 
necessary to change the liquid refrigerant to a vapor (latent heat). As the heat to 
accomplish this change comes from the air around the coil, the heat removed from the 
air is 165.6 Btu per pound of methyl chloride evaporated in the coil. When the refriger- 
ant is circulated at 2 Ib per minute, 2 X 165.6, or 331.2 Btu per minute are removed from 
the air, or refrigerating effect is produced at the rate of 331.2 -5- 200, or 1.65 tons. 

4 Calculate the dew-point, wet-bulb, relative humidity and absolute hu- 
midity of air in equilibrium at 100 F with pure lithium chloride solution of 
density 1.270. 

From Table 8 the concentration of a solution of density 1.270 at 100 F is 18.0 M. From 
Table 7 the dew-point of 18 M lithium chloride at 100 F is 43.7 F. From Table 6, 
Chapter 1, the partial pressure of water over the solution is 0.2858 in. of Hg, the absolute 
humidity is 42.00 grains per pound dry air, and the wet-bulb is 65.8 F. The relative 
humidity is 14.0 per cent. 

5 Calculate the boiling point, and freezing point of 18 M lithium chloride 
solutions. 

From Table 10, boiling point (standard) is 285.8 F, freezing point is 58.1 F. The salt 
precipitated on cooling to this temperature has the composition LiCl-2H 2 0. 

6 Calculate the heat of vaporization of 1 Ib of water from a large amount of 
lithium chloride solution at the boiling point. 

The heat of boiling is equal to the heat of mixing plus the heat of boiling pure water at 
the same temperature. The heat of mixing from Table 10 at 18 M and 285.8 F is (145 
0.186 X 285.8) = 92 Btu per pound. The heat of vaporization of water from steam 
tables at 285.8 F is 920 Btu per pound. Therefore the heat of vaporization of water 
from the solution is 920 -f 92 = 1012 Btu per pound. 

7 One thousand pounds of air per minute at 100 F dry -bulb with a dew-point 
of 70 F and a relative humidity of 39 per cent is passed over 18 M lithium chloride 
solution. The rate of flow of the solution is 200 gpm and the entering tempera- 
ture is 80 F. The air leaves the absorber at 85 F dry-bulb and dew-point of 
35 F. Calculate (a) the heat to be removed from the lithium chloride solution 

49 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



to maintain these conditions, and (6) the temperature rise of the solution in 
passing through the absorber. 

a. The heat content of the entering air: From Table 6, Chapter 1, weight of vapor at 
70 F dew-point is 0.01574 ib times heat content of steam at 100 F dry-bulb is 1104.2 
(Table 8, Chapter 1) equals 17.41 Btu per pound plus heat content of dry air at 100 F 
is 24.0 (Table 6, Chapter 1) resulting in heat content of mixture as 41.41 Btu per pound. 

Similarly, the heat content of the leaving air: Weight of vapor at 35 F dew-point is 
0.004262 X 1097.5 4.68 Btu per pound plus heat content of dry air at 85 F is 20.39 
resulting in heat content of mixture as 25.07 Btu per pound. 

Heat to be extracted from air is 1000 X (41.41 - 25.07) = 16,340 Btu per minute. 
Add to this the heat of mixing of 18M lithium chloride at 80 F equals 145 - (0.186 X 
80) = 130 Btu per pound (Table 10) or for 1000 Ib of air X (0,01574 - 0.00426) X 130 = 
1494 Btu per minute. Heat to be removed from solution is 16,340 + 1494 = 17,834 
Btu per minute. 

6. The weight of solution circulated is 200 X 1.275 (Table 8) X 8.33 = 2124 Ib per 
minute. Its heat capacity is 2124 X 0.631 (Table 10) = 1340 Btu per minute per degree 
Fahrenheit. The temperature rise is 17,834 * 1340 = 13.31 F. 



Chapter 3 

PHYSICAL AND PHYSIOLOGICAL PRINCIPLES 
OF AIR CONDITIONING 

Vitiation of Air, Heat Regulation in Man, Effects of Heat, 
Effects of Cold and Temperature Changes, Acclimatization, 
Effective Temperature Index of Warmth, Optimum Air Condi- 
tions, Winter and Summer Comfort Zone, Optimum Humid- 
ity, Air Quality and Quantity, Air Movement and Distribution, 
Natural and Mechanical Ventilation, Heat and Moisture 
Losses, Ultra- Violet Radiation and lonization, Recirculation 
and Ozone, Ventilation Standards 

VENTILATION is defined in part as " the process of supplying or 
removing air by natural or mechanical means to or from any space." 
(See Chapter 45,) The word in itself implies quantity but not necessarily 
quality. ^ From the standpoint of comfort and health, however, the 
problem is now considered to be one of securing air of the proper quality 
rather than of supplying a given quantity. 

The term air conditioning in its broadest sense implies control of any or 
all of the physical or chemical qualities of the air. More particularly, it 
includes the simultaneous control of temperature, humidity, movement, 
and purity of the air. The term is broad enough to embrace whatever 
other additional factors may be found desirable for maintaining the 
atmosphere^of occupied spaces at a condition best suited to the physio- 
logical requirements of the human body. 

VITIATION OF AIR 

Under the artificial conditions of indoor life, the air undergoes certain 
physical and chemical changes which are brought about by the occupants 
themselves. The oxygen content is somewhat reduced, and the carbon 
dioxide slightly increased by the respiratory processes. Organic matter, 
which is usually perceived as odors, comes from the nose, mouth, skin 
and clothing. The temperature of the air is increased by the metabolic 
processes, and the humidity raised by the moisture emitted from the skin 
and lungs. There is also a marked decrease in both positive and negative 
ions in the air of occupied rooms but the significance of this factor is 
still questionable 1 . 

Contrary to old theories, the usual changes in oxygen and carbon 
dioxide are of no physiological concern because they are much too small 
even under the worst conditions. The amount of carbon dioxide in air is 

Changes in Ionic Content in Occupied Rooms Ventilated, by Natural and Mechanical T Methods by 
C. P. Yaglou, L. C. Benjamin and S. P. Choate (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 191). 

51 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

often used in ventilation work as an index of odors of human origin, but 
the information it affords rarely justifies the labor involved in making the 
observation 2 - 3 . Little is known of the identity and physiological effects of 
the organic matter given off in the process of respiration. The former 
belief that the discomfort experienced in confined spaces was due to some 
toxic volatile matter in the expired air is now limited, in the light of 
numerous researches, to the much less dogmatic view that the presence of 
such a substance has not been demonstrated. The only certain fact is 
that expired and transpired air is odorous and offensive, and it is capable 
of producing loss of appetite and a disinclination for physical activity. 
These reasons, whether esthetic or physiological, call for the introduction 
of a certain minimum amount of clean outdoor air to dilute the odoriferous 
matter to a concentration which is not objectionable. 

A certain part of the dissemination of disease in confined spaces is 
caused by the emission of pathogenic bacteria from infected persons. 
Droplets sprayed into the air in talking, coughing, sneezing, etc., do not 
all fall immediately to the ground within a few feet from the source, as it 
was formerly believed. The large droplets do, of course, but minute 
droplets less than 0.1 mm. in diameter evaporate to dryness before the}' 
fall the height of a man. Nuclear residues from such sources, which may 
contain infective organisms drift long distances with the air currents and 
the virus may remain alive long enough to be transmitted to other persons 
in the same room or building. Wells 4 recovered droplet nuclei from 
cultures of resistant micro-organisms a week after inoculation into a 
tight chamber of 300 cu ft capacity. Typical organisms of infections of 
the upper respiratory tract (pneumococcus type I, B. diphtheriae, Strep- 
tococcus hemolyticus, and Streptococcus viridans) were found to die 
out quite soon when exposed to light and air, and could be recovered from 
the air in small numbers only 48 hours after inoculation/ Organisms 
typical of the intestinal tract (B. coli, B. typhosus, B. paratyphosus, 
A. and B. dysenteriae) were not recovered 12 hours after inoculation. 

The significant factors in infection are believed to be the numbers, of 
infective organisms encountered, the frequency of exposure, and the 
resistance of the individual including the degree of acquired immunity. 
The probability of encountering a sufficient number of organisms to 
break down the natural body defense is related to the air space per person 
and the quantity of clean air supplied. Except in badly ventilated rooms, 
the danger is believed to be "much contracted in space, limited in time 
and restricted to comparatively few diseases." 5 

^ Practical possibilities in sterilizing air supplies by the use of ultra- 
violet light are now being studied 6 . 

The primary factors in air conditioning work, in the absence of any 
specific contaminating source, are temperature, radiation, drafts and 

TRAJ?sSo^ A Vol C1 ^9 nS 19S d Ai J 6 ?{ 8triblltion ' by R C Houghten and J. L. Blackshaw (A.S.H.V.E. 
v i n l e o nti iQ7A n R W\ r ements, *>y c - p - Yaglou, E. C. Riley and D. I. Coggins (A.S.H.V.E. TRANSACTIONS, 

vol. <U, laoO, p. L63). 

oi^"* 001 * Infection and Sanitary Air Control, by W. F. Wells, (Journal Industrial Hygiene, November, 

oOj. 

B^TcS iV N 1 l? U i9&f nd Hygiene ' by Muton J- Rosenau (6th edition, pp. 909-917, D. Appleton- 
slTsa^^gO) 2 ' ^ OU Exp Sed t0 UttxBrVtolet Radiation in Air. by W. F. Wells, and G. M. Fair (Science, 

52 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 



body odors. As compared with these physical factors, the chemical 
factors are, as a general rule, of secondary importance. 

HEAT REGULATION IN MAN 

The importance of the thermal factors arises from the profound in- 
fluence which they exert upon body temperature, comfort and health. 
Body temperature depends on the balance between heat production and 
heat loss. The heat resulting from the combustion of food within the 
body maintains the body temperature well above that of the surrounding 
air. At the same time, heat is constantly lost from the body by radiation, 
conduction and evaporation. Since, under ordinary conditions, the body 
temperature is maintained at its normal level of about 98.6 F, the heat 
production must be balanced by the heat loss. In healthy persons this 
takes place automatically by the action of the heat regulating mechanism. 

According to the general view, special areas in the skin are sensitive to 
heat and cold. Nerve courses carry the sense impressions to the brain and 
the response comes back over another set of nerves, the motor nerves, to 
the musculature and to all the active tissues in the body, including the 
endocrine glands. In this way, a two-sided mechanism controls the body 
temperature by (1) regulation of internal heat production (chemical 
regulation) , and (2) regulation of heat loss by means of automatic varia- 
tion in the rate of cutaneous circulation and the operation of the sweat 
glands (physical regulation). The mechanisms of adjustment are complex 
and little understood at the present time. Coordination of these dif- 
ferent mechanisms seems to vary greatly with different air conditions. 

With rising air temperatures up to 75 F or 80 F, metabolism, or internal 
heat production, decreases slightly 7 , probably by an inhibitory action on 
heat producing organs, especially the adrenal glands, which seem to exert 
the major influence on basic combustion processes in the body. The blood 
capillaries in the skin become dilated by reflex action of the vasomotor 
nerves, allowing more blood to flow into the skin, and thus increase its 
temperature and consequently its heat loss. The increase in peripheral 
circulation is at the expense of the internal organs. If this method of 
cooling is not in itself sufficient, the stimulus is extended to the sweat 
glands which allow water to pass through the surface of the skin, where it 
is evaporated. This method of cooling is the most effective of all, as long 
as the humidity of the air is sufficiently low to allow for evaporation. In 
high humidities, where the difference between the dew-point temperature 
of the air and body temperature is not sufficient to allow rapid evapora- 
tion, equally good results may be obtained by increasing the air move- 
ment, and hence the heat loss by conduction and evaporation. 

In cold environments, in order to keep the body warm there is an actual 
increase in metabolism brought about partly by voluntary muscular con- 
tractions (shivering) and partly by an involuntary reflex upon the heat 
producing organs. The surface blood vessels become constricted, and 
the blood supply to the skin is curtailed by vasomotor shifts to the internal 
organs in order to conserve body heat. The sweat glands become inactive. 



7 Heat and Moisture Losses from the Human Body and Their Relation to Air Conditioning Problems, 
by F. C. Houghten, W. W. Teague, W. E. Miller and W. P. Yant (A.S.H.V.E. TRANSACTIONS, Vol. 35, 
1929, p. 245). 

53 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



EFFECTS OF HEAT 

Although the human organism is capable of adapting itself to variations 
in environmental conditions, its ability to maintain heat equilibrium is 
limited. The upper limit of effective temperature to which the human 
organism is capable of adapting itself without serious discomfort or 
injury to health is 90 deg ET for men at rest and between 80 and 90 deg 
ET for men at work depending upon the rate of work. Within these 
limits a new equilibrium is established at a higher body temperature level 
through a chain of physiological adjustments. The heat regulating center 
fails, when the external temperature is so abnormally high that bodily 
heat cannot be eliminated as fast as it is produced. Part of it is retained 
in the body, causing a rise in skin and deep tissue temperature, an increase 
in the heart rate, and accelerated respiration. (See Table 1.) In extreme 

TABLE 1. PHYSIOLOGICAL RESPONSES TO HEAT OF MEN AT REST AND AT WORK* 









MEN AT WOBK 




ACTUAL 


MEN AT RBST 


90,000 FT-LB of WORK PER HOUE 


EfTccxtni 
TBJCP. 


TEMP. 
IDio 
FAHR) 


Rise in 
Rectal 
Temp. 

Fahrper 
Hour) 


Increase 
in Pulse 
Rate 
(gate per 
Min per 
Hour) 


Loss in Body 
Weight by 
Perspiration 
(Lb perHr) 


Total Work 
Accomplished 
(Ft-Lb) 


Rise in 
Body Temp. 
(Deg Fair 
per Hr) 


Increase in 
Pulse Rate 
(Beat* per 
Min per Hr) 


Approximate 
Loss in Body 
Wt. by Per- 
spiration (Lb 
per Hr) 


60 











225,000 


0.0 


6 


0.5 


70 




o.o 


6 


6.2~ 


225,000 


0.1 


7 


0.6 


80 


96.1 


0.0 





0.3 


209,000 


0.3 


11 


0.8 


85 


96.6 


0.1 


i 


0.4 


190,000 


0.6 


17 


1.1 


90 


97.0 


0.3 


4 


0.5 


153,000 


1.2 


31 


1.5 


95 


97.6 


0.9 


15 


0.9 


102,000 


2.3 


61 


2.0 


100 


99.6 


2.2 


40 


1.7 


67,000 


4.0 


103b 


2.7 


105 


104.7 


4.0 


83 


2.7 


49,000 


6.0*> 


158b 


3.5*> 


110 





5.9b 


137b 


4.0*> 


37,000 


8.5b 


237* 


4.4b 



Data by A.S.H.V.E. Research Laboratory. 

bCompnted va!ue from exposures lasting less than one hour. 

heat, the metabolic rate is markedly increased owing to the excessive rise 
in body temperature 8 , and a vicious cycle results which may eventually 
lead to serious physiologic damage. 

Examples of this are met with in unusually hot summer weather and in 
hot industries where the radiant heat from hot objects renders heat loss 
from the body by radiation and convection impossible. Consequently, 
the workers depend entirely on evaporation for the elimination of body 
heat. They stream with perspiration and drink liquids abundantly to 
replace the loss. 

One of the deleterious effects of high temperatures is that the blood is 
diverted from the internal organs to the surface capillaries, in order to 
serve in the process of cooling. This affects the stomach, heart, lungs and 
other vital organs, and it is suggested that the feeling of lassitude and 
discomfort experienced is due in part to the anaemic condition of the brain 
The stomach loses some of its power to act upon the food, owing to a 



54 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 

diminished secretion of gastric juice, and there is a corresponding loss in 
the antiseptic and antifermentive action which favors the growth of 
bacteria in the intestinal tract 9 . These are considered to be the potent 
factors in the increased susceptibility to gastro-intestinal disorders in hot 
summer weather. The victim may lose appetite and suffer from indiges- 
tion, headache and general enervation, which may eventually lead to a 
premature old age. 

In warm atmospheres, particularly during physical work, a considerable 
amount of chloride is lost from the system through sweating. The loss of 
this substance may lead to attacks of cramps, unless the salts are replaced 
in the drinking water. In order to relieve both cramps and fatigue, 
Moss 10 recommends the addition of 6 grams of sodium chloride and 4 grams 
of potassium chloride to a gallon of water. 

The deleterious physiologic effects of high temperatures exert a power- 
ful influence upon physical activity, accidents, sickness and mortality. 
Both laboratory and field data show clearly that physical work in warm 
atmospheres is a great effort, and that production falls progressively as 
the temperature rises. The incidence of industrial accidents reaches a 
minimum at about 68 F, increasing above and below that temperature. 
Sickness and mortality rates increase progressively as the temperature 
rises. 

EFFECTS OF COLD AND TEMPERATURE CHANGES 

The action of cold on human beings is not well known. Cold affects the 
human organism in two ways: (1) through its action on the body as a 
whole, and (2) through its action on the mucous membranes of the upper 
respiratory tract. Little exact information is available on the latter. 

On exposure to cold r the loss of heat is increased considerably and only 
within certain limits is compensation possible by increased heat produc- 
tion and decreased peripheral circulation. The rectal temperature often 
rises upon exposure to cold but the pulse rate and skin temperature fall. 
The blood pressure increases, owing to constriction in the peripheral 
vessels. Just how cold affects health is not well understood. It imposes 
an extra load upon the heat-producing organs to maintain body tempera- 
ture. The strain falls largely upon digestion, metabolism, blood circu- 
lation, and the kidneys, and indirectly upon the nervous system 11 . 

Although the seasonal increase in morbidity and mortality sets in with 
the approach of cold weather and subsides in the warm summer months, 
little is known of the specific causative factors and their mechanism of 
action. Over-crowding of buildings, overheated rooms, lack of venti- 
lation, and close personal contacts are frequently held responsible for our 
winter ills, but the evidence is not conclusive. 

In extremely cold atmospheres compensation by increased metabolism 
becomes inadequate. The body temperature falls and the reflex irritability 
of the spinal cord is markedly affected. The organism may finally pass 
into an unconscious state which ends in death. 

innueucc of Effective Temperature upon Bactericidal Action of Gastro-intestinal Tract, by Arnold and 
Brody (Proceedings Society Exp. Biol. Mcd. Vol. 24, 1927, p. 832). 

10 Some Effects of High Air Temperatures upon the Miner, by K. N. Moss (.Transactions Institute of 
Mining Engineers, Vol. 66, 1924, p. 284). 
"Loc. Cit. Note 5. 

55 



HEATING VENTIIATING AIR CONDITIONING GUIDE 1938 

Cannon showed that excessive loss of heat is associated with increased 
activity of the adrenal medulla 12 . The extra output of adrenin hastens 
heat production which protects the organism against cooling. Bast 13 
found a degeneration of thyroid and adrenal glands upon exposure to cold. 

A moderate amount of variability in temperature is known to be 
beneficial to health, comfort, and the performance of physical and mental 
work. On the other hand, extreme changes in temperature, such as those 
experienced in passing from a warm room to the cold air out-of-doors, 
appear to be harmful to the tissues of the nose and throat which are the 
portals for the entry of respiratory diseases. 

Experiments show that chilling causes a constriction of the blood 
vessels of the palate, tonsils, throat, and nasal mucosa, which is accom- 
panied by a fall in the temperature of the tissues. On re-warming, the 
palate and throat do not always regain their normal temperature and 
blood supply. This anaemic condition favors bacterial activity and it 
probably plays a part in the disposition of common cold and other 
respiratory diseases. It is believed that the lowered resistance is due to a 
diminution in the number and phagocytic activity of the leucocytes 
(white blood cells) brought about by exposure to cold and by changes 
in temperature. 

Sickness records in industries seem to strengthen this belief. The 
Industrial Fatigue Research Board of En'gland 14 found that in workers 
exposed to high temperatures and to changes in temperature, namely, 
steel melters, puddlers, and general laborers, there is an excess of all 
sickness, the excess among the puddlers being due chiefly to respiratory 
diseases and rheumatism. The causative factor was not the heat itself 
but the sudden changes in temperature to which the workers were exposed. 
The tin-plate millmen who were not exposed to chills, since they work 
almost continuously throughout the shift, had no excess of rheumatism 
and respiratory diseases. On the other hand, the blast-furnacemen, who 
work mostly in the open, showed more respiratory sickness than the steel 
workers. This experience in British factories is well in accord with the 
findings in American industries 15 - 16 . According to these data the highest 
pneumonia death rate is associated with dust, extreme heat, exposure to 
cold, and to sudden changes in temperature. 

ACCLIMATIZATION 

Acclimatization and the factor of psychology are two important in- 
fluences in air conditioning which cannot be ignored. The first is man's 
ability to adapt himself to changes in air conditions; the second is an 
intangible matter of habit and suggestion. 

Some persons regard the unnecessary endurance of cold as a virtue. 



^ f. Cannon, A. Guerido, S. W. Britten 

- Bast * j - s - Supernaw ' B - Lieberman and j - Munr 

Lol h d e on) n ^ Sted Industry ' by H ' M ' Vernon industrial Fatigue Research 

telWfarf Bulletin, 
Bloomfield < 



56 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 

They believe that the human organism can adapt itself to a wide range of 
air conditions with no apparent discomfort or injury to health. In the 
light of the present knowledge of air conditioning these views are not 
justified. Acclimatization to extreme conditions involves a strain upon 
the heat regulating system and it interferes with the normal physiologic 
functions of the human body. Thousands of years in the heat of Africa 
do not seem to have acclimatized the Negro to a temperature averaging 
80 F. The same holds true of northern races with respect to cold, although 
the effects are mitigated by artificial control. All this seems to indicate 
that adaptation to an environment averaging between 60 and 80 F is a 
very primitive trait 17 . 

Within these limits, however, there does occur a definite adaptation to 
external temperature level. People and animals raised under conditions 
of tropical moist heat have a lower rate of heat production than do those 
who grow up in cooler environments. This causes them to stand chilling 
poorly as they are unable to quickly increase internal combustion to keep 
up the body temperature. For this reason they have trouble standing 
the cold, stormy weather of the temperate zones, and when exposed to it 
are very susceptible to respiratory infections. Likewise, people living in 
cool climates suffer greatly in the moist heat of the tropics until their 
adrenal activity has slowed down. Within a couple of years, however, 
they find themselves standing the heat much better and disliking cold. 
They become acclimated by a definite change in the combustion level 
within the body 18 . 

In certain individuals the psychologic factor is more powerful than 
acclimatization. A fresh air fiend may suffer in a room with windows 
closed regardless of the quality of the air. As a matter of fact, instances 
are known in which paid subjects refused to stay in a windowless but 
properly conditioned experimental chamber because the atmosphere felt 
suffocating to them upon entering the room. 

EFFECTIVE TEMPERATURE INDEX OF WARMTH 

Sensations of warmth or cold depend, not only on the temperature of 
the surrounding air as registered by a dry-bulb thermometer, but also 
upon the temperature indicated by a wet-bulb thermometer. Dry air at 
a relatively high temperature may feel cooler than air of considerably 
lower temperature with a high moisture content. Air motion makes any 
moderate condition feel cooler. 

On the other hand, in cold environments an increase in humidity 
produces a cooler sensation. The dividing line at which humidity has no 
effect upon warmth varies with the air velocity and is about 46 F (dry- 
bulb) for still air and about 51, 56 and 59 F for air velocities of 100, 300 
and 500 fpm, respectively. Radiation from cold or warm surfaces is 
another important factor under certain conditions. 

Combinations of temperature, humidity and air movement which 
induce the same feeling of warmth are called thermo-equivalent con- 



"Civilization and Climate, by Ellsworth Huntington, Yale University Press, 1924. 
"Air Conditioning in its Relation to Human Welfare, by C. A. Mills (A.S.H.V.E. TRANSACTIONS, Vol. 
40, 1934, p. 289). 

57 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 




I jj 



-50 



FIG. 1. EFFECTIVE TEMPERATURE CHART SHOWING NORMAL SCALE OF EFFECTIVE 

TEMPERATURE. APPLICABLE TO INHABITANTS OF THE UNITED STATES UNDER 

FOLLOWING CONDITIONS: 



i/*** c . ustomar y indoor clothing. B. Activity: Sedentary or light muscular work. C. Heating 
Methods: Convection type. i.e. warm air, direct steam or hot water radiators, plenum systems. amnn * 

58 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 

ditions. A series of tests 19 - 20 22 at the A.S.H.V.E. Research Labora- 
tory, Pittsburgh, established the equivalent conditions met with in 
general air conditioning work. This scale of thermo-equivalent conditions 
not only indicates the sensation of warmth, but also determines the 
physiological effects on the body induced by heat or cold. For this reason, 
it is called the effective temperature scale or index. 

Effective temperature is an empirically determined index of the degree 
of warmth perceived^ on exposure to different combinations of tempera- 
ture, humidity, and air movement. It was determined by trained subjects 
who compared the relative warmth of various air conditions in two ad- 
joining conditioned rooms by passing back and forth from one room to 
the other. 

Effective temperature is not in itself an index of comfort, except under 
ordinary humidity conditions (30 to 60 per cent) when the individual is 
least conscious of humidity. Moist air at a comparatively low tem- 
perature, and dry air at a higher temperature may each feel as warm as 
air of an intermediate temperature and humidity, but the comfort ex- 
perienced in the three air conditions would be different, although the 
effective temperature is the same. 

Air of proper warmth may, for instance, contain excessive water vapor, 
and in this way interfere with the normal physiologic loss of moisture 
from the skin, leading to damp skin and clothing and producing more or 
less discomfort; or the air may be excessively dry, producing appreciable 
discomfort to the mucous membrane of the nose and to the skin which 
dries up and becomes chapped from too rapid loss of moisture. 

The numerical value of the effective temperature index for any given 
air condition is fixed by the temperature of calm (15 to 25 fpm air move- 
ment) and saturated air which induces a sensation of warmth or cold like 
that of the given condition. Thus, any air condition has an effective 
temperature of 60 deg, for instance, when it induces a sensation of warmth 
like that experienced in calm air at 60 deg saturated with moisture. The 
effective temperature index cannot be measured directly but it is com- 
puted from the dry- and wet-bulb temperature and the velocity of air 
using- charts (see Figs. 1 or 2, 3 and 4) or tables. The accuracy in esti- 
mating effective temperature is 0.5 F, because the human organism 
cannot perceive smaller temperature differences. Therefore, there is no 
justification in trying to read chart values closer than 0,5 F, as this 
implies fictitious accuracy. 

The charts shown in Figs. 1, 2, 3 and 4 apply to average normal^and 
healthy persons adapted to American living and working conditions. 
Application is limited to sedentary or light muscular activity, and to 
rooms heated by the usual American convection methods (warm air, 
central fan and direct hot water and steam heating systems) in which the 
difference between the air and wall surface temperatures may not be too 



"Determining Lines of Equal Comfort, by F. C. Houghten and C. P. Yaglou (A.S.H.V.E. TRANS- 
ACTIONS, Vol. 29, 1923, p. 361). 

'"Cooling Effect on Human Beings by Various Air Velocities, by F. C. Houghten and C. P. Yaglou 
(A.S.H.V.E. TRANSACTIONS, Vol. 30, 1924, p. 193). 

^Effective Temperature with Clothing, by C. P. Yaglou and W. E. Miller (A.S.H.V.E. TRANS- 
ACTIONS, Vol. 31, 1925, p. 89). 

^Effective Temperature for Persons Lightly Clothed and Working in Still Air, by F. C. Houghten, W. W. 
Teague and W. E. Miller (A.S.H.V.E. TRANSACTIONS, Vol. 32, 1926, p. 315). 

59 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



great. The charts do not apply to rooms heated by radiant method such 
as British panel system, open coal fires and similar usages. They will 
probably not apply to races other than the white or perhaps to inhabitants 
of other countries where the living conditions, climate, heating methods, 
and clothing are materially different than those of the subjects employed 
in experiments at the Research Laboratory. 




jo SNIIVMO 



In rooms in which the average wall surface temperature is considerably 
below or above air temperature, a correction must be applied to the 
readings of the dry-bulb thermometer to allow for such negative or 
positive radiation. In Fig. 5 is given the cooling effect of cold walls as 
determined at the A.S.H.V.E. Research Laboratory" by trained subjects 



l McDennott 



60 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES or AIR CONDITIONING 

passing back and forth from a small experimental room having three cold 
walls, to a control room with walls and air at the same temperature. 

It can be seen in Fig. 5 that with air and walls at 70 F in the control 
(warm wall room), the cooling effect of three cold walls at 55 F of the 
experimental room was 4 F. Therefore, for the same feeling of warmth, 




3 S * 

aiv AHQ jo amod *ad 3arusiow jo SNivyo 



the temperature in the experimental room should be increased to 74 F. 
The reverse would hold in rooms with high-wall surface temperature; a 
lower air temperature would be required to compensate for positive 
radiations to the occupants. 



61 



HEATING VENTIULTING AIR CONDITIONING GUIDE 1938 



OPTIMUM Affi CONDITIONS 

No single comfort standard can be laid down which would meet^ every 
need. There is an inherent individual variation in the sensation of 
warmth or comfort felt by persons when exposed to an identical atmos- 
pheric condition. The state of health, age, sex, clothing, activity, and 




AHQ JO QNnOd H3d 3Ur>JLSIOfl JO SNIVdO 



the degree of acquired adaptation seem to be the important factors 
affecting the comfort standards, 

Since the prolonged effects of temperature, humidity and air move- 
ment on health are not known to the same extent as their effects on com- 
fort, the optimum conditions for health may not be identical with those 
for comfort. On general physiologic grounds, however, the two do not 
differ greatly since this is in accordance with the efficient operation of the 

62 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 

heat regulating mechanism of the body. This belief is strengthened by 
results of studies on premature infants over a four-year period 24 . By 
adjusting the temperature and humidity so as to stabilize the body tem- 
perature of these infants, the incidence of diarrhoea and mortality was 
decreased, gains in body weight increased and infections were reduced 
to a minimum. 

Winter Comfort Zone and Comfort Line 

In Fig. 6 is shown the A.S.H.V.E. winter comfort zone which was 
determined experimentally with large groups of men and women subjects 
wearing customary indoor winter clothing. The extreme comfort zone 
includes conditions between 60 and 74 deg ET in which one or more of the 
experimental subjects were comfortable. The average comfort zone 




WALL TEMPERATURE, DEG FAHR 



FIG. 5. COOLING EFFECT OF THREE COLD WALLS IN A SMALL EXPERIMENTAL ROOM, 

AS DETERMINED BY COMPARISON WITH SENSATIONS IN A ROOM OF UNIFORM 

WALL AND AIR TEMPERATURE 

includes conditions between 63 and 71 deg ET conducive to comfort in 
50 per cent or more of the experimental subjects. The most popular 
effective temperature was found to be 66 deg, and was adopted by the 
Society 25 as the winter comfort line for individuals at rest wearing custom- 
ary winter clothing. 

The comfort line separates the cool air conditions to its left from the 
warm air conditions to its right. Under the air conditions existing along 
or defined by the comfort line, the body is able to maintain thermal 



"Application of Air Conditioning to Premature Nurseries in Hospitals, by C. P. Yaglou, Philip Drinker 
and K. D. Blackfan (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 383). 

How to Use the Effective Temperature Index and Comfort Charts (A.S.H.V.E. TRANSACTIONS, 
Vol. 38, 1932, p. 410). 

63 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



90 



, STILL AIR 

' Air Mcveirent or Turbulence 15 to 25 ft. per min. 
I ; A.S H.V.E. COMFORT CHART 

(Cot>\riht 1934} 



Average Winter Comfort Zone 
'- - Average Winter Comfort Line 
K//V///I Average Summer Comfort Zone 
Average Summer Comfort Line 




70 80 90 TOO 

Pry Bulb Temperature F 

FIG. 6. A.S.H.V.E. COMFORT CHART FOR AIR VELOCITIES OF 15 TO 25 FPM 
(STILL AIR)*>, 

gfn^o^ 

8hSS. aPP y t0 "' department stores ^ d Belike whe?e the expo^elrie^^ 

equilibrium with its environment with the least conscious sensation to the 
mdmdual, or with the minimum phsyiologic demand on the heat regulat- 
ing mechanism. This environment involves not only the condition of the 
air with respect to temperature and humidity, but also the condition of 
the surrounding objects and wall surfaces. The comfort zone tests were 

Zon^r^^^^^ 

CA.S.H.V.E. 



64 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 

made in rooms with wall surface temperatures approximately the same as 
the room dry-bulb temperature. For walls of large area having unusually 
high or low surface temperatures, however, a somewhat lower or higher 
range of effective temperature is required to compensate for the increased 
gain or loss of heat to or from the body by radiation as shown in Fig. 5 
(See also Chapter 41). 

The average winter comfort line (66 deg ET) applies to average 
American men and women living inside the broad geographic belt across 
the United States in which central heating of the convection type is 
generally used during four to eight months of the year. It does not apply 
to rooms heated by radiant energy, rooms with excessive glass area or 
rooms with poorly insulated or cold walls. Even in the warm south and 
southwestern climates, and in the very cold north-central climate of the 
United States, ^the comfort chart would probably have to be modified 
according to climate, living and working conditions, and the degree of 
acquired adaptation. 

In densely occupied spaces, such as classrooms, theaters and audi- 
toriums, somewhat lower temperatures may be necessary than those 
indicated by the comfort line on account of counter-radiation between the 
bodies of occupants in close proximity 28 . 

The sensation of comfort, insofar as the physical environment is con- 
cerned, is not absolute but varies considerably among certain individuals. 
Therefore, in applying the air conditions indicated by the comfort line, 
it should not be expected that all the occupants of a room will feel per- 
fectly comfortable. When the winter comfort line is applied in accordance 
with the foregoing recommendations, the majority of the occupants will 
be perfectly comfortable, but there will always be a few who would feel 
a bit too cool and a few a bit too warm. These individual differences among 
the minority should be counteracted by suitable clothing. 

Air conditions lying outside the average comfort zone but within the 
extreme comfort zone may be comfortable to certain persons. In other 
words, it is possible for half of the occupants of a room to be comfortable 
in air conditions outside the average comfort zone, but in the majority of 
cases, if not in all, these conditions will be well within the extreme comfort 
zone as determined experimentally. 

The comfort chart (Fig. 6) applies to adults between 20 and 70 years 
of age living in the northeastern parts of the United States. For pre- 
maturely born infants, the optimum temperature varies from 100 F to 
75 F, depending upon the stage of development. The optimum relative 
humidity for these infants is placed at 65 per cent 29 . No data are yet 
available on the optimum air conditions for full term infants and young 
children up to school age. Satisfactory air conditions for these age 
groups are assumed to vary from 75 F to 68 F with natural indoor humidi- 
ties. For school children, the studies of the New York State Commission 
on Ventilation place the optimum air conditions at 66 F to 68 F tempera- 
ture with a moderate humidity (not specified) and a moderate but not 
excessive amount of air movement (not specified) 30 . 



Loc. Cit. Note 27. 
aLoc. at. Note 24. 
"Ventilation (Report N. Y. State Commission on Ventilation. E. P. Button and Co., N. Y., 1923). 

65 



HEATING VENTIIIATINO AIR CONDITIONING GUIDE 1938 

Satisfactory comfort conditions for men at work are found to vary from 
40 deg to 70 deg ET, depending upon the rate of work and amount of 
clothing worn 31 . In hot industries, 80 deg ET is considered the upper 
limit compatible with efficiency, and, whenever possible, this should be 
reduced to 70 deg ET or less. 

Summer Comfort Zones 

The summer comfort zone is much more difficult to fix than the winter 
zone owing to the complicating factor of sweating in warm weather. A 
given air condition which is comfortable for persons with dry skin and 
clothing may prove too cold for those perspiring, as is the case, for 
instance, with employees and customers in a cooled store, restaurant, or 
theater, on a warm summer day. The conditions to be maintained in 
different types of public buildings depend to a large extent upon_ the oc- 
cupants' length of stay and upon the prevailing outdoor condition. 

In Fig. 6 is shown the summer comfort zone for exposures of 3 hours or 
more, after adaptation has taken place. The average zone extends from 
66 to 75 deg ET, with a comfort line at 71 deg ET, as determined at the 
Harvard School of Public Health 32 . These effective temperatures average 
about 4 deg higher than those found in winter when customary winter 
clothing was worn. The variation from winter to summer is probably due 
partly to adaptation to seasonal weather and partly to differences in the 
clothing worn in the two seasons. 

The best effective temperature (for exposures lasting 3 hours or more) 
was found to follow the average monthly outdoor temperature more 
closely than the prevailing outdoor temperature. It remained at approxi- 
mately the same value in July, August and September, and although the 
average monthly temperature did not vary much, the prevailing outdoor 
temperature ranged from 70 F to 99.5 F. A decrease in the optimum 
temperature became apparent only when the prevailing outdoor tempera- 
ture fell to 66 F, which is below the customary room temperature in the 
United States for summer and winter. 

Crowding the experimental chamber lowered the comfortable effective 
temperature from 70.8 deg when the gross floor area per occupant was 
44 sq ft and the air space 380 cu ft, to 69.4 deg when the floor area was 
reduced to 14 sq ft and the air space to 120 cu ft per occupant. 

The basic summer comfort zone, shown in Fig. 6 has more academic 
than practical significance. It prescribes conditions of choice for con- 
tinuous exposures, as in homes, offices, etc., without regard to costs, 
prevailing outdoor air conditions, and temperature contrasts upon 
entering or leaving the cooled space. A great number of persons seem to 
be content with a higher plane of indoor temperature, particularly when 
the matter of first cost and cost of operation of the cooling plant is given 
due consideration. 

According to previous investigations 33 , an indoor temperature of about 
80 F with relative humidities below 55 per cent, or 74.5 deg ET and lower, 
result in satisfactory comfort conditions in the living quarters of a residence, 

Loc. Cit. Note 22. 
Loc. Cit. Note 27. 



. . . 

v f ^i? 1 ? of Summer (Doling in the Research Residence for the Summer of 1934, by A. P. Kratz, S. Konzo, 
M. K. Fahnestock and E. L. Broderick (A.S.H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 207). 

66 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES or AIR CONDITIONING 

and while this condition is not representative of optimum comfort it 
provides for sufficient relief in hot weather to be acceptable to the majority 
of users. Experience in a number of air conditioned office buildings, 
including the New Metropolitan Life Building in New York 34 , indicates 
that a temperature of about 80 F with a relative humidity between 45 and 
55 per cent (73 to 74.5 deg ET) is generally satisfactory in meeting the 
requirements of the employees. 

In artificially cooled theaters, restaurants, and other public buildings 
where the period of occupancy is short, the contrast between outdoor and 
indoor air conditions becomes the deciding factor in regard to the tem- 
perature and humidity to be maintained. The object of cooling such 
places in the summer is to provide sufficient relief from the heat without 
causing sensations of chill or intense heat on entering and leaving the 
building. 

Effective temperatures as high as 75 F at times have been found satis- 
factory in very warm weather. There are two schools of thought con- 
cerning the relation between temperature and humidity to be maintained. 
For a given effective temperature some engineers including the operators 
of cooling plants favor a comparatively low temperature with a high 
humidity as this results in a reduction of refrigeration requirements. 
Preliminary experiments at the A.S.H.V.E. Laboratories 35 would seem to 
indicate no appreciable impairment of comfort with relative humidities 
as high as 80 per cent, provided the effective temperature is between 
70 and 75 deg, 

The second school favors a higher dry-bulb temperature, according^ to 
the prevailing outdoor dry-bulb, with a comparatively low humidity 
(well below 50 per cent) ; the main purpose being to reduce temperature 
contrasts upon entering and leaving the cooled, space and to keep the 
clothing and skin dry. This second scheme requires more refrigeration 
with the present conventional type of apparatus. 

Current practice in theatres, restaurants, etc., follows a schedule 
similar to that shown in Table 2, This schedule should be used^with con- 
siderable judgment depending on the occupancy and local climatic 
conditions. There are some indications that a definite indoor effective 
temperature may be applicable throughout the cooling season, but 
other observations seem to show that changing indoor conditions are 
desirable with violently changing outdoor weather conditions. It is, in 
fact, questionable whether entirely satisfactory air conditions could be 
adduced for practical use to meet the changing requirements of patrons 
from the time they enter to the time they leave a cooled space. Too 
many uncontrollable variables enter into the problem. Work now going 
on at the A.S.H.V.E. Laboratories and other interested institutions may 
throw considerable light on this complex problem. _^ 

For cooled banks and stores where the customers come and go spending 



*The Air Conditioned System of the New Metropolitan Building First Summer's Experience, by W. J. 
McConnell and I. B. Kagey (A.S.H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 217). 

^Comfort Standards for Summer Air Conditioning, by F. C. Houghten and Carl Gutberlet (A.S.H.V.E. 
TRANSACTIONS, Vol. 42, 1936, p. 215). Cooling Requirements for Summer Air Conditioning, by F. C. 
Houghten, F. E. Giesecke, Cyril Tasker and Carl Gutberlet (A.S.H.V.E. JOURNAL SECTION, Heating, 
Piping and Air Conditioning, December, 1936, p. 681). 

67 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 2. DESIRABLE INSIDE CONDITIONS ix SUMMER CORRESPONDING 
TO OUTSIDE TEMPERATURES** 

Occupancy Over 40 Min 

INSIDE AIR CONDITIONS 



DEC F 


Effective Dry-Bulb Wet-Bulb 
Temperature Deg F , Deg F 


Dew-Point 
DegF 


Relative Humid- 
ity Per Cent 


100 


75 83 
75 82 
75 81 
75 i 80 


66 

i 67 

68 
70 


56 
59 
61 
65 


40 
45 
51 
60 


95 


74 
74 
74 
74 
74 


82 
81 
80 
79 
78 


64 
66 
67 
68 
70 


53 
57 
60 
62 
66 


36 

44 
51 
57 
68 


90 

i 

i 


73 
73 
73 
73 


81 
80 
79 
78 


63 
64 
66 
67 


52 

54 
59 
61 


36 
41 
50 
56 


85 : 

1 

1 


72 
72 
72 
72 


80 
79 

78 
77 


61 
63 
64 
66 


48 
53 
56 
60 


32 
41 
46 
56 


80 


71 
71 
71 
71 


78 
77 
76 
75 


61 
63 
64 
66 


49 
54 
57 
61 


36 
45 
52 
61 



^Applicable to individuals engaged in sedentary or light muscular activity. 

but a few minutes in the cooled space, observations 36 indicate a schedule 
about 1 deg dry-bulb or effective temperature higher than that shown in 
Table 2. Laboratory experiments with exposures of 2 to 10 min indicate 
temperatures 2 to 10 F higher than those in Table 2 but with much lower 
relative humidities. 

It should be kept in mind that southern people, with their more sluggish 
heat production and lack of adaptability, will demand a comfort zone 
several degrees higher than that for the more active people of northern 
climates. Instead of the summer comfort line standing at 71 deg as here 
given, it was found to be much higher for foreigners in Shanghai where 
climatic conditions are similar to those of our gulf states. This difference 
in adaptability of people forms a very real problem for air conditioning 
engineers. Cooling of theaters, restaurants, and other public buildings in 
southern climates cannot be based on northern standards without con- 
siderable modification. 

Optimum Humidity 

Just what the optimum range of humidity is, is a matter of conjecture. 
1 here seems to exist a general opinion, supported by some experimental 
and statistical data, that warm, dry air is less pleasant than air of a 



- bv J- H - Walker (Heating 



68 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 

moderate humidity, and that it dries up the mucous membranes in such 
a way as to increase susceptibility to colds and other respiratory dis- 
orders 37f 38> 39t Owing to the cooling effect of evaporation, higher tem- 
peratures are necessary, and this condition may lead to discomfort and 
lassitude. Moist air, on the other hand, interferes with the normal 
evaporation of moisture from the skin, and again may cause a feeling of 
oppression and lassitude, especially when the temperature is also high. 
For the premature infant, a high relative humidity of about 65 per cent is 
demonstrably beneficial to health and growth 40 until the infants reach a 
weight of about 5 Ib. No such clear-cut evidence exists in the case of 
adult persons. In the comfort zone experiments of the A.S.H.V.E. 
Research Laboratory, the relative humidity was varied between the 
limits of 30 and 70 per cent approximately, but the most comfortable 
range has not been determined. In similar experiments at the Harvard 
School of Public Health, the majority of the subjects were unable to 
detect sensations of humidity (i.e., too high, too low, or medium) when 
the relative humidity was between 30 per cent and 60 per cent with 
ordinary room temperatures. This is in accord with studies by Howell 41 , 
Miura 42 and others. 

The limitation of the comfort zones in Fig. 6 with respect to humidity 
must not be taken too seriously. Relative humidities below 30 per cent 
may prove satisfactory from the standpoint of comfort, so long as ex- 
tremely low humidities are avoided. From the standpoint of health, 
however, the consensus seems to favor a relative humidity between 40 and 
60 per cent. In mild weather such comparatively high relative humidi- 
ties are entirely feasible, but in cold or sub-freezing weather they are 
objectionable on account of condensation and frosting on the windows. 
They may even cause serious damage to certain building materials of the 
exposed walls by condensation and freezing of the moisture accumulating 
inside these materials. Unless special precautions are taken to properly 
insulate the affected surfaces, it will be necessary to reduce the degree of 
artificial humidification in sub-freezing weather to less than 40 per cent, 
according to the outdoor temperature. Information on the prevention of 
condensation on building surfaces is given in Chapter 7. The principles 
underlying humidity requirements and limitations are discussed more 
fully elsewhere 43 . 

The purpose of artificial humidification may be easily defeated by 
failure to change the spray water of the humidifier at least daily. Where 
this condition occurs, the air is characterized by a lack of freshness, and 
under extreme conditions by a musty, sour odor in the conditioned space. 



"Reactions of the Nasal Cavity and Post-Nasal Space to Chilling of the Body Surface, by Mudd, Stuart, 
et al (Journal Experimental Medicine, 1921, Vol. 34, p. 11). 

^Reactions of the Nasal Cavity and Post-Nasal Space to Chilling of the Body Surfaces, by A. Goldman, 
et al and Concurrent Study of Bacteriology of Nose and Throat (Journal Infectious Diseases, 1921, Vol. 29, 
p. 151). 

S9 The Etiology of Acute Inflammations of the Nose, Pharynx and Tonsils, by Mudd, Stuart, et al (Am. 
Otol., Rhinol., and Laryngol., 1921). 

Loc. Cit. Note 24. 

^Humidity and Comfort, by W. H. Howell (The Science Press, April, 1931). 

^Effect of Variation in Relative Humidity upon Skin Temperature and Sense of Comfort, by U. Miura 
(American Journal of Hygiene, Vol. 13, 1931, p. 432). 

^Humidification for Residences, by A. P. Kratz, University of Illinois (Engineering Experiment Station 
Bulletin No. 230, July 28, 1931). 

69 



HEATING VENTIIATING AIR CONDITIONING GUIDE 1938 

Affi QUALITY AND QUANTITY 
Air Quality 

In occupied spaces in which the vitiation is entirely of human origin, 
the chemical composition of the air, the dust, and often the bacteria con- 
tent may be dismissed from consideration so that the problem consists in 
maintaining a suitable temperature with a moderate humidity, and in 
keeping the atmosphere free from objectionable odors. Such unpleasant 
odors, human or otherwise, can be easily detected by persons entering the 
room from clean, odorless air. 

In industrial rooms where the primary consideration is the control of 
air pollution (dusts, fumes, gases, etc.), or contamination not removable 
at the source of production, the clean air supply must be sufficient to 
dilute the polluting elements to a concentration below the physiological 
threshold (see Chapters 4 and 26). 

Air Quantity 

The air supply to occupied spaces must always be adequate to satisfy 
the physiological requirements of the occupants. It must be sufficient to 
maintain the desired temperature, humidity, and purity with reasonable 
uniformity and without drafts. In many practical instances there are 
two air quantities to be considered, (a) outdoor air supply, and (b) total 
air supply. The difference between the two gives the amount of air to be 
recirculated. 

When the only source of contamination is the occupant, the minimum 
quantity of outdoor air needed appears to be that necessary to remove 
objectionable body odors, or tobacco smoke. The concentration of body 
odor in a room, in turn, depends upon a number of factors, including 
socio-economic status of occupants, outdoor air supply, air space allowed 
per person, odor adsorbing capacity of air conditioning processes, tem- 
perature, and other factors of secondary importance. With any given 
group of occupants and type of air conditioner the intensity of body odor 
perceived upon entering a room from relatively clean air was found to 
vary inversely with the logarithm of outdoor air supply and the logarithm 
of the air space allowed per person* 

The minimum outdoor air supply necessary to remove objectionable 
body odors under various conditions, as determined experimentally at the 
Harvard School of Public Health 44 , is given in Table 3. 

Outdoor air requirements for the removal of objectionable tobacco 
smoke odors have yet to be determined. Practical values in the field vary 
from 5 to 15 cfm per person; this air quantity may and should be a part 
of that necessary for other requirements, i.e., removal of body odors, heat, 
moisture, etc. 

The total quantity of air to be circulated through an enclosure is 
governed largely^ by the needs for controlling temperature and air dis- 
tribution when either heating or cooling is required. The factors which 
determine total air quantity include the type and nature of the building, 
locality, climate, height of rooms, floor area, window area, extent of 
occupancy, and last but not least, the method of distribution. 

Serious difficulties are often encountered in attempting to cool a room 

**Loc. Cit Note 3. 

70 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 



with a poor distribution system or with an air supply which is too small to 
result in uniform distribution without drafts. Some systems of distribu- 
tion produce drafts with but a few degrees temperature rise, while other 
systems operate successfully with a temperature rise as high as 35 F. 
The total air quantity introduced in any particular case is inversely pro- 
portional to the temperature rise, and depends largely upon the judgment 
and ingenuity of the engineer in designing the most suitable system for the 
particular conditions. 

TABLE 3. MINIMUM OUTDOOR AIR REQUIREMENTS TO REMOVE OBJECTIONABLE 

BODY ODORS 

(Provisional values subject to revision upon completion of work) 



TYPE OP OCCUPANTS 



AIR SPACE PER 
PEBSON Cu FT 



OUTDOOR* AIR SUPPLY 
CFM ?BR PERSON 



Heating season with or without recirculation. Air not conditioned. 



Sedentary adults of average socio-economic status 
Sedentary adults of average socio-economic status 


100 
200 


25 
16 


Sedentary adults of average socio-economic status 
Sedentary adults of average socio-economic status. 


300 
500 


12 
7 


Laborers 


200 


23 








Grade school children of average class 


100 


29 


Grade school children of average class 
Grade school children of average class 


200 
300 


21 
17 


Grade school children of average class 


500 


11 


Grade school children of poor class 


200 


38 


Grade school children of better class 


200 


18 


Grade school children of best class 


100 


22 



Heating season. Air humidified by means of centrifugal humidifier. Water 
atomization rate 8 to 10 gph. Total air circulation SO cfm per person. 



Sedentary Adults 


200 


12 





Summer season. Air cooled and dehumidified by means of a spray dehumidifier. 
Spray water changed daily. Total air circulation 80 cfm per person. 



Sedentary Adults 


200 


<4 





a Impressions upon entering room from relatively clean air at threshold odor intensity. 



The changes in moisture content resulting from occupation in the 
atmosphere of a room supplied with various volumes of outside air is 
shown in Fig. 7. Data are given for an adult, 5 ft 8 in. in height, weighing 
150 Ib and having a body surface of 19.5 sq ft and for a child, 12 years of 
age, 4 ft 7 in. in height weighing 76.6 Ib and having a body surface area 
of 12.6 sq ft. Also given in Fig. 7 is the temperature of incoming air 
necessary to maintain a room temperature of either 70 or 80 F as indicated 
assuming that there is no heat gain or loss to the room by transmission 
through the walls, solar radiation or other sources. 

71 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



AIR MOVEMENT AND DISTRIBUTION 

Stagnant warm air, no matter how pure, is not stimulating and it 
detracts to some extent from the quality of air. Experience, and recent 
field studies by the A.S.H.V.E. Research Laboratory 45 place the desirable 
air movement between 15 and 25 fpm under ordinary room temperatures 
during the heating season. Objectionable drafts are likely to occur when 
the velocity of the air current is 40 fpm and the temperature of the air 
current 2 F or more below the customary winter room temperature. 
Higher velocities are not objectionable in the summer time when the air 



i i i 

ADULTS IN 80 F AIR 



!>CHILDREN IN 80 F AIR 



.ADULTS IN 70 F AIR 
(^.CHILDREN IN 70 F AIR 



CHILDREN IN 80 F AIR 



ULTS IN 80 F AIR 



CHILDREN IN 70 F AIR 



ADULTS IN 70 F AIR 




12 16 20 24 28- 

RATE OF AIR SUPPLY 
CUBIC FEET PER MINUTE PER OCCUPANT 

FIG. 7. RELATION AMONG RATE OF AIR CHANGE PER OCCUPANT, MOISTURE CONTENT 
OF ENCLOSURE, AND DRY-BULB TEMPERATURE OF INCOMING AIR 

temperature exceeds 80 F. Variations in air movement and temperature 
in different parts of occupied rooms are often indicative of relative air 
distribution. The work of the A.S.H.V.E. Research Laboratory indicates 
that an air movement between 15 and 25 fpm with a temperature variation 
of 3 F or less in different parts of a room, 36 in. above floor, insure satis- 
factory distribution. Considerable evidence was obtained in these tests 
to show that measurements of carbon dioxide are not essential for the 
study of air distribution, or for indirect measurements of outdoor air 



^Classroom Drafts in Relation to Entering Air Stream Temperature, by F. C. Houghten, 
Cart Gutberlet and M. F. Lichtenfels (A.S.H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 268). 



, H. H. Trimble, 



72 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES or AIR CONDITIONING 



TABLE 4. RELATION BETWEEN METABOLIC RATE AND ACTIVITY* 



ACTIVITY 


HOTJRLT META- 
BOLIC RATE FOB 
AYG. PERSON OB 
TOTAL HEAT 
DISSIPATED, 
BTU PER HOUR 


HOURLT 

SENSIBLE 
HEAT 
DISSIPATED, 
BTU PER 
HOUR 


HOURLY 
LATENT 
HEAT 
DISSIPATED, 
BTU PER 
HOUR 


MOISTURE DISSIPATED, 
PER HOUR 


GRAINS 


LB 


Average Person Seated at Rest 1 .. 
Average Person Standing at Rest 1 


384 
431 


225 
225 


159 
206 


1070 
1390 


0.153 

0.199 


Tailor 2 


482 


225 


257 


1740 


0.248 


Office Worker Moderately Active 


490 


225 


265 


1790 


0.256 


Clerk, Moderately Active, 












Standing at Counter. 


600 


225 


375 


2530 


0.362 


Book Binder 2 . 


626 


225 


401 


2710 


0.387 


Shoe Maker 2 ; Clerk, Very Active 












Standing at Counter 


661 


225 


436 


2940 


0.420 


Pool Player 


680 


230 


450 


3040 


0.434 


Walking^ mph 3 . 4 ; Light 












Dancing 


761 


250 


511 


3450 


0.493 


Metalworker 2 


862 


277 


585 


3950 


0.564 


Painter of Furniture 2 . 


876 


280 


596 


4020 


0.575 


Restaurant Serving, Very Busy.. 


1000 


325 


675 


4560 


0.651 


Walking 3 mph 8 


1050 


346 


704 


4750 


0.679 


Walking 4 mph 8 . *; Active 
Dancing, Roller Skating. 


1390 


452 


938 


6330 


0.904 


Stone Mason 2 


1490 


490 


1000 


6750 


0.964 


Bowling 


1500 


490 


1010 


6820 


0.974 


Man Sawing Wood 2 . 


1800 


590 


1210 


8170 


1.167 


Slow Run 4 


2290 










Walking 5 mph 8 


2330 










Vgry Severe Exercise** 


2560 










Maximum Exertion Different 












People 4 . 


3000 to 4800 



















aMetabolism rates noted based on tests actually determined from the following authoritative sources: 
iA.S.H.V.E. Research Laboratory; *Becker and Hamalainen; 'Douglas, Haldane, Henderson and Schneider; 
^Henderson and Haggard; and "^Benedict and Carpenter. Metabolic rates for other activities estimated. 
Total heat dissipation integrated into latent and sensible rates by actual tests for metabolic rates up to 
1250 Btu per hour, and extrapolated above this rate. Values for total heat dissipation apply for all atmos- 
pheric conditions in a temperature range from approximately 60 to 90 F dry-bulb. Division of total heat 
dissipation rates into sensible and latent heat holds only for conditions having a dry-bulb temperature of 
79 F. For lower temperatures, sensible heat dissipation increases and latent heat decreases, while for 
higher temperatures the reverse is true. 



TABLE 5. 



DEGREES OF PERSPIRATION FOR PERSONS SEATED AT REST UNDER 
VARIOUS ATMOSPHERIC CONDITIONS 



DEGREE OF PERSPIRATION* 


ATMOSPHERIC CONDITION 


95 Per Cent Relative 
Humidity 


20 Per Cent Relative 
Humidity 


E.T. 


D.B. 


W.B. 


E.T. 


D.B. 


W.B. 


Forehead clammy .. 


73.0 
73.0 
79.0 
80.0 
84.5 
88.0 
88.5 


73.6 
73.6 
79.7 
80.8 
85.4 
89.0 
89.5 


72.4 
72.4 
78.4 
79.4 
84.0 
87.6 
88.1 


75.0 
75.0 
81.0 
87.0 
86.5 
94.0 
90.0 


87.0 
87.0 
97.5 
109.4 
108.5 
125.2 
116.0 


60.7 
60.7 
67.5 
75.2 
74.6 
85.4 
79.5 


Body clammy.. . . 
Body damp . . - 


Beads on forehead 
Body wet. 


Perspiration on forehead runs and drips 
Perspiration runs down body- . 





Forty per cent of subjects registered degree of perspiration equal to or greater than indicated. 

73 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



! 1 ' ' 


-H~~*" 
JTU- 


* U 










1 ! ' | ' M ~ 

' I ' ! ' ' i 
, ' ' ' ^ 

^ ; "'-y^ i - 


p-r- : , i i I n I , J | 
.1 ;':,';!' i i > L 

1 ' ' ' ' ^ 

: JT ''^ 

! i ' i >^r i M$ 

' l^^^i : 

ni;b/ffl li 


wm 

&L-"--- 

:^::::fe 

"Ib 


' 
, 1 
-^-H- 


1 ' ' 

"t~h~ 

L-in 

jf 


r4- 

T^ 


^ 


d 


^c 

-r 

4 


s 

ft 


jT 

s f 

' I : / / 
1 'A A 

H4# 

!/ / j 

/ j 

I/I ' 1 1 1 


ijr^i.y- * \ 

/.SiA'fo i -r^ 
lJ TT !1 f MM 

/ ' i /[ * ' ' i 
7 y- -HI H-I 

M j , 1 , . | 1 


TTrmTr 

b 

- ;^ 
::"::__ b 


44- 


1 III 




1 j J 

i-LJL 


1 


Y 


1 

- 


^M 4- 




p> 



I 11 



. 



fefe g *3sf s 
^g| 3 .|I|g 

8" w o d ^sf Sc 
?2,S ^fel^^a 



8 8 8 

ooio-^<ON- 
ClJt>s"S5D NVW 39VU3AV 0d 'BH H3d Til* "VIOL 



05 B 



oooooo 
oooooo 
ocor*<o 

OJT35SBD NVW 39VH3AV tJO 




oo 
oo 
evi 

U3d TO IB TV1QI 



74 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 



TABLE 6. DEGREES OF PERSPIRATION FOR PERSONS AT WORK UNTER VARIOUS 
ATMOSPHERIC CONDITIONS 

Work Rate 83,000 Ft Lb per Hour 



DEGREE OF PERSPIRATION" 


95 Per Cent Relative 
Humidity 


20 Per Cent Relative 
Humidity 


E. T. 


D.B. 


W.B. 


E. T. 


D.B. 


W.B 


Forehead clammy 


59.0 
50.0 
60.0 
68.0 
69.0 
78.5 
79.0 


59.4 
50.2 
60.3 
68.5 
69.6 
79.3 
79.8 


58.3 
49.3 
59.3 
67.5 
68.5 
78.0 
78.5 


69.5 
57.0 
62.5 
76.0 
71.0 
82.0 
81.0 


80.5 
61.6 
69.6 
91.0 
82.8 
100.5 
99.8 


56.5 
44.2 
49.5 
63.4 
53.0 
70.2 
69.0 


Body clammy 
Body damp . . 
Beads on forehead. 


Body w^t 


Perspiration on forehead runs and drips 
Perspiration runs down body 





ATMOSPHERIC CONDITION 



aForty per cent of subjects registered degree of perspiration equal to or greater than indicated. 

supply, which can be obtained more conveniently from the increase in 
moisture content of the ventilating current. 



HEAT AND MOISTURE GIVEN UP BY HUMAN BODY 

In conditioning air for comfort and health it is necessary to know the 
rate of sensible and latent heat liberation, from the human body, which in 
conjunction with other heat loads (see Chapters 5 and 7) determine the 
capacity of the conditioner. The data in common use are those of the 
A.S.H.V.E. Research Laboratory 46 shown in Figs. 8, 9, 10 and 11. Other 
useful data are given in Tables 4, 5 and 6, which are self-explanatory. 

ULTRA-VIOLET RADIATION AND IONIZATION 

In spite of the rapid advances in the field of air conditioning during the 
past few years, the secret of reproducing indoor atmospheres of as 
stimulating qualities as those existing outdoors under ideal weather con- 
ditions, has not as yet been found. Extensive studies have failed to 
elucidate the cause of the stimulating quality of country air, qualities 
which are lost when such air is brought indoors and particularly when it 
is handled by mechanical means. Ultra-violet light and ionizatlon have 
been suggested but the evidence so far is inconclusive or negative 47 . 



* 6 Thermal Exchanges between the Bodies of Men Working and the Atmospheric Environment, by F. C. 
Houghten, W. W. Teague, W. E. Miller and W. P. Yant (American Journal of Hygiene, Vol. XIII, No. 2. 
March, 1931, pp. 415-431). 

47 Changes in Ionic Content in Occupied Rooms, Ventilated by Natural and Mechanical Methods, by 
C. P. Yaglou, L. C. Benjamin and S. P. Choate (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 191). Physio- 
logic Changes During Exposure to Ionized Air, by C. P. Yaglou, A. D. Brandt and L. C. Benjamin (A.S. 
H.V.E. TRANSACTIONS, Vol. 39, 1933, p. 357). Diurnal and Seasonal Variations in the Small Ion Content 
of Outdoor and Indoor Air, by C. P. Yaglou and L. C. Benjamin (A.S.H.V.E. TRANSACTIONS, Vol. 40, 
1934, p. 271). The Nature of Ions in Air and Their Possible Physiological Effects, by L/. B. Loeb (A.S. 
H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 101). The Influence of Ionized Air upon Normal Subjects, by 
L. P. Herrington (Journal Clinical Investigation, 14, January, 1935). The Effect of High Concentrations 
of Light Negative Atmospheric Ions on the Growth and Activity of the Albino Rat, by L. P. Herrington 
and Karl L. Smith (Journal Ind. Hygiene, 17, November, 1935). Subjective Reactions of Human Beines 
to Certain Outdoor Atmospheric Conditions, by C.-E. A. Winslow and L. P. Herrington (A.S.H.V.E. 
TRANSACTIONS, Vol. 42, 1936, p. 119). 

75 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



^1000 










"-i i"< * t' 'jx^T F 


H 










I , ! M ,' " 


U. 












gonn 










, . y^; -, - 


900 




















, L. I , I ' ,' | , ! ' , ! I 


jf i i _; 


Ann 
































, . i/Lj 












1 ; ' i ' / ' i 


i . / ^ -5000 


S *VA/> 








1 ' j/ 1 f 














/ ^ z 










i i X ' 




o 








rii , | /! : 


j ; . ; j>" _ _, ^ - 


< 600 








1 . 'i 1 : i 1 !/| . | i 














/My^ ^ - 












fj y i X^^T - 


50O 




















i ' ! J ' ' / 




g 












2 t 










^~ yf _3000 


cf 40 




-j- 




! ' / / '' 


y~" ;-" 


1 I 




--U. 


--J-H 


f ~ l ~ .x T ~^~^^ ^ 


-r- 


300: 




x 


| 




r r--E-2ooo 


* 
























=**oo 


L 






L.-JL-L-f?-^ 


-g__X = 


at 


-h- 






4L*' i *-l L.J. 


i- E-iooo 














<!> 













DRY BULB TEMPELRATURE *FAHR. g 

FIG. 10. LATENT HEAT AND MOISTURE Loss FROM THE HUMAN BODY BY EVAPORATION 
IN RELATION TO DRY-BULB TEMPERATURE FOR STILL AIR CoNDiTioNS a 



/- - A .T Men working 66,150 ft-Ib per hour. Curve B Men working 33,075 ft-lb per hour. Curve 

C Men working 16,638 ft-lb per hour. Curve D Men seated at rest. Curves A and C drawn from data 
at a dry-bulb temperature of 81.3 F only and extrapolating the relation between Curves B and D which 
were drawn from data at many temperatures. 




45 50 55 60 65 70 75 
DRY BULB TEMPERATURE *FAHR. 



OSS * ROM ra i5 HUMAN BODY BY EVAPORATION, RADIATION AND CON- 
RELATION TO DRY-BULB TEMPERATURE FOR STILL AIR CONDITION^ 



76 



CHAPTER 3. PHYSICAL & PHYSIOLOGICAL PRINCIPLES OF AIR CONDITIONING 



NATURAL AND MECHANICAL VENTILATION 

Under favorable conditions natural ventilation methods properly com- 
bined with means for heating may be sufficient to provide for the fore- 
going objectives in homes, uncrowded offices, small stores, etc. 

In large offices, large school rooms, and in public and industrial build- 
ings, natural ventilation is uncertain and makes heating difficult. The 
chief disadvantage of natural methods is the lack of control ; they depend 
largely on weather and upon the velocity and direction of the wind. 
Rooms on the windward side of a building may be difficult to heat and 
ventilate on account of drafts, while rooms on the leeward side may not 
receive an adequate amount of air from out-of-doors. The partial vacuum 
produced on the leeward side under the action of the wind may even 
reverse the flow of air so that the leeward half of the building has to take 
the drift of the air from the rooms of the windward half. Under such 
conditions no outdoor air would enter through a leeward window opening, 
but room air would pass out. 

In warm weather natural methods of ventilation afford little or no 
control of indoor temperature and humidity. Outdoor smoke, dust and 
noise constitute other limitations of natural methods. 

RECmCULATION AND OZONE 

The amount of recirculated air may be varied to suit changes in weather 
and seasonal requirements, so as to conserve heat in winter and refrig- 
eration in summer, but the saving in operating cost should not be obtained 
at the expense of air quality. 

Ozone has been used for deodorizing recirculated air by oxidation or 
masking. Under favorable conditions some success is possible but from 
the practical standpoint it is difficult to regulate the ozone output so as to 
just neutralize undesirable odors at all times during the occupancy of a 
room. The difficulties appear to be mainly due to a wide variability in 
the rate of ozone disappearance in different rooms, or in the same room at 
different times, according to the characteristics of a room, the absolute 
humidity, impurities in the air, number and type of occupants, and 
probably other factors which require considerable study before ozone can 
be safely and economically applied. 

The allowable concentrations in the breathing zone are very small, 
between 0.01 to 0.05 parts of 3 per million parts of air. These are much 
too small to influence bacteria. Higher concentrations are associated 
with a pungent unpleasant odor and considerable discomfort to the 
occupants. One part per million causes respiratory discomfort in man, 
headaches and depression, lowers the metabolism, and may even lead to 
coma 48 . 

Toilets, kitchens, and similar rooms, in buildings using recirculation, 
should be ventilated separately by mechanical exhaust in order to prevent 
objectionable odors from diffusing into other parts of the building. 



**The British Medical Journal. Editorial. June 25, 1932, p. 1182. See also Loc. Cit. Note 5. 

77 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 
PROBLEMS IN PRACTICE 

1 What are the most comfortable air conditions? 

Comfort standards are not absolute, but they are greatly affected by the physical con- 
dition of the individual, and the climate, season, age, sex, clothing, and physical activity. 
For the northeastern climate of the United States, the conditions which meet the require- 
ments of the majority of people consist of temperatures between 68 and 72 F in winter 
and between 70 and 85 F in summer, the latter depending largely upon the prevailing 
outdoor temperature. The most desirable relative humidity range seems to be between 
30 and 60 per cent. 

2 Are the optimum conditions for comfort identical with those for health? 

There are no absolute criteria of the prolonged effects of various air conditions on health. 
For the present it can be only inferred that bodily discomfort may be an indication of 
adverse conditions leading to poor health. 

3 Given dry-bulh and wet-bulb temperatures of 76 F and 62 F, respectively, 
and an air velocity of 100 fpm, determine: (l) effective temperature of the 
condition; (2) effective temperature with calm air; (3) cooling produced hy the 
movement of the air. 

(1) In Fig. 1 draw line AB through given dry- and wet-bulb temperatures. Its inter- 
section with the 100 ft velocity curve gives 69 deg for the effective temperature of the 
condition. (2) Follow line AB to the right to its intersection with the 20 fpm velocity 
line, and read 70.4 deg for the effective temperature for this velocity or so-called still air. 
(3) The cooling produced by the movement of the air is 70.4 - 69 = 1.4 deg ET. 

4 Assume that the design of an air conditioning system for a theater is to he 
based on an outdoor dry-bulb temperature of 95 F and a wet-bulb temperature 
of 78 F with an indoor relative humidity of 50 per cent. According to Table 2, 
the dry-bulb temperature in the auditorium should be 80 F. Estimate the 
sensible and latent heat given up per person. 

The sensible heat given up per person per hour may be obtained from Fig. 9. With an 
abscissa value of 80 F, Curve D for men seated at rest gives a value (on the ordinate 
scale) of 220 Btu per person per hour as the sensible heat loss. The latent heat given up 
by a person seated at rest may be obtained from Fig. 10. With an abscissa value of 80 F, ' 
Curve D indicates a latent heat loss of 175 Btu per hour (left hand scale) or a moisture 
loss of 1190 grains per hour (right hand scale). 

5 Neglecting the gain or loss of heat by transmission or infiltration through 
walls, windows and doors, how many cubic feet of outside air, with dry- and 
wet-bulb temperatures of 65 F and 59 F, respectively, (63.1 deg ET) must be 
supplied per hour to an auditorium containing 1000 people in order that the 
inside temperature shall not exceed 75 F dry-bulb and 65 F wet-bulb? 

Figs. 9 and 10 give 265 Btu sensible heat and 905 grains of moisture per person with a 
dry-bulb temperature of 75 F in the auditorium. Therefore, 265,000 Btu of sensible 
heat and 905,000 grains of moisture will be added to the air in the auditorium per hour. 

Taking 0,24 as the specific heat of air, 2.4 Btu per pound of air will be absorbed in 
raising the dry-bulb temperature from 65 to 75 F, and 265,000 -4- 2.4 - 110,400 Ib of 
air or 110,400 X 13.4 = 1,479,000 cfh of air will be required. This is equivalent to 
1,479,000 -5- (1000 X 60) = 24.7 cfm per person. 

The ^moisture content of the inside air is 76 grains per pound of dry air and that of the 
outside condition is 65 grains. From a psychrometric chart the increase in moisture 
content will therefore be 11 grains per pound of dry air. Hence 905,000 + 11.0 = 82,300 
Ib of air at the specified condition will be required. This is equivalent to 82,300 X 13 4 
- 1,103,000 cfh of air or 1,103,000 -- (1000 X 60) - 18.4 cfm of air per person. 

The higher volume of 24.7 cfm per person will be required to keep the dry-bulb tem- 
perature from rising above the 75 F specified. The wet-bulb temperature will therefore 
not rise to the maximum of 65 F. 



78 



Chapter 4 

AIR POLLUTION 

Classification of Air Impurities, Dust Concentrations, Air 

Pollution and Health, Occlusion of Solar Radiation, Smoke 

and Air Pollution Abatement, Dust and Cinders, Nature's 

Dust Catcher 

THE particulate impurities which contribute to atmospheric pollution 
include carbon from the combustion of fuels, particles of earth, sand, 
ash, rubber tires, leather, animal excretion, stone, wood, rust, paper, 
threads of cotton, wool, and silks, bits of animal and vegetable matter, 
and pollen. Microscopic examination of the impurities in city air shows 
that a large percentage of the particles are carbon. 

CLASSIFICATION OF AIR IMPURITIES 

The most conspicuous sources of atmospheric pollution may be classi- 
fied arbitrarily according to the size of the particles as dusts, fumes, and 
smoke. Dusts consist of particles of solid matter varying from 1.0 to 150 
microns in size, (micron = 0.001 millimeter or 1/25,000 in.) Fumes 
t include particles resulting from chemical processing, combustion, explo- 
sion, and distillation, ranging from 0.1 to 1.0 micron in size. The word 
fumes may be applied also to mixtures of mists (liquid droplets) and gases 
as acid mists. Smoke is composed of fine soot or carbon particles, usually 
less than 0.1 micron in size, which result from incomplete combustion of 
carbonaceous materials, such as. coal, oil, tar, and tobacco. In addition 
to carbon and soot, smoke contains unconsumed hydrocarbon gases, 
sulphur dioxide, carbon monoxide, and other industrial gases capable of 
injuring property, vegetation, and health. 

The lines of demarcation in these three classifications are neither sharp 
nor positive, but the distinction is descriptive of the nature and origin of 
of the particles, and their physical action. Dusts settle without appre- 
ciable agglomeration, fumes tend to aggregate, smoke to diffuse. Particles 
which approach the common bacteria in size about 1 micron are 
difficult to remove from air and are apt to remain in suspension unless 
they can be agglomerated by artificial means. The term fly-ash is usually 
applied to the microscopic glassy spheres which form the principal solid 
constituent of the effluent gases from powdered-coal fired furnaces. 
Cinders denote the larger solid constituents which may be entrained by 
furnace gases. 

It is well established that particles larger than about 1 micron are 
unlikely to remain suspended in air currents of moderate strength. Only 

79 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



violent air motion will sustain them in air long enough for them to be 
breathed. This means that, in hygenic problems, the engineer is con- 
cerned mostly with suspensions of particles comparable to the common 



D!AM. 
OF 
PAR- 
TICLES 

m 

HICW113 




SCALE OF 
ATMOSPHERIC 
IMPURITIES 


RATE OF 
SETTLING 
IN F.PM. 
FOR 
SPHERED 
OF 
DENSITY I 
AT 10* F. 


NUMBER 
OFPAR- 
TICIESW 
OMECUFT 


SURFACE 
AREA IN 
SQUARE 
INCHES 


LAWS OF SETTLING 
IN RELATION TO 
PARTICLE SIZE 
(LINES OF DEMARCATION APPRO*.) 


AIR CONTAINING 
.0006 GRAINS OF 
IMPURITIES PER 
CU.FT.(BEM31T<-0 


8000 
600O 


p" :.. -i."..--. r., -td 








| PARTICLES SETTLE WITH CONSTANT VELOCITY | 


PARTICLES FALL WITH 
INCREASING VELOCITY 


4000 
000 

1000 
800 
600 

400 
200 

100 
SO 


=^=^rz|: 


790 


.075 


.000)65 


C = 24.9VD7 


oVelocity ctn/sc. 
CWelocity ft/mm. 

dDiam of par- 
ticle in cm. 

D*Diam. of par- 
ticlt in Microns 

r Radius of par- 
ticle in cm. 

g-SSlcm/aec* 
acceleration 

s,- Density of 
particle 

s z =Density of Air 
(Very Small 
relative to s,) 

57* Viscosity of 
air in poises 
-!814xlO~ T for 
o.r at 70* F. 

(Mean free 
path of gas 
molecules ) 




'^^FP- 


^H-J^^^ 


555 


g 


00_0!3__ 
.003653 


- 


-1 




-L." S )D < 

e* ^,!ui O: 




75 


3 

A | 

-f*i 




i ^ 


ff 




iza ^ 

O u 

r-^r * 


STOKES 
LAW 

FOR AIR AT 70 *F. 

c -300,460s,d* 
C -.0059ZS.D* 

CUNNINGHAM'S 


60 
40 

20 

10 
8 




3| 




stgss 


^ 


tf 


532 


600 
75000 


.0073 

.0365 * 
|& 1N.SQ. 




I s 




JGp 3 ij 


" 


^- 






5 




si 5 " s i 


t; 


s 


o* 


1 






^1< 




1 


G 

Z 
1 










-| 


m 






148 
JOT 5" 


600.000 
75X10* 


.073 
.365 3 




3 


tf 


s! 


H u* 


CE 




| 


a. 


:( 


53 UJ o 


S 

a 




.6 

.4 

.2 

1 






^^H 


-K 


_jjjU 






002=1.4" 


60XI0 7 


8 
.73 


FACTOR 


ifl 




y 


s 








PCRHR. 
MOtn-64 


75x10* 


3.65 


f 1 "! 


ft S 


2 


< 






C'-C OF STOKES IAW 
K -.8 TO .86 


uJ 


UJ 


s f 




? k 






1 


te. 


ci 




I 


^ 




.01 
















PER HR. 




i.e IN.SO. 


PARTICLES N 
GAS MOL 

BROWN IAN 
MOVEMENT 

A= Vff 3^7 


1OVE LIKE 
&CULES 

A- Distance of 
motion m time t 

R-Gas constant 
-0.316x10'' 

T- Absolute 
Temperature 

N* Number of Gas 
molecules in 
onemoi-edOSxlO 23 





fii 


-^ 


Sti 


ri 


& 







73XI0 11 




UJ 

y: 




en 

t 

5 


-a*? 

s< 


o5 


; 5 


hJ 




a| 8 8 









15- f 


o 




.OOI 

















60XI0 13 


73.0 








'-.5 8 j 


n 






2 


U Zh 


^.< w & 











365 S 
2.5350. FT. 





f 


-y 


irl- y 




- 










5 







Compiled by W. G. Frank and Copyrighted. 
FIG. 1. SIZES AND CHARACTERISTICS OF AIR-BORNE SOLIDS 

bacteria in size. A notable exception to this size limitation is the common 
hay-fever producing pollen such as that from rag-weed. Pollen grains 
may be anything from fragments 15 microns in diameter to whole pollens 
25 microns or more in size. Since the lower limit of visability to the 



CHAPTER 4. AIR POLLUTION 



TABLE 1. APPROXIMATE LIMITS OF INFLAMMABILITY OF SINGLE GASES AND VAPORS 
IN AIR AT ORDINARY TEMPERATURES AND PRESSURES** 



GAS OR VAPOR 



LOWER LIMIT 
VOLTJMB IN PER CENT 



HIGHER LIMIT 
VOLUME IN PER CENT 



Hydrogen 


4 1 


74 o 


Ammonia 


16 


27 


Hydrogen sulphide 


43 


46 


Carbon disulphide 


1 


50 


Carbon monoxide 


12 5 


74 


Methane 


5 3 


14 


Methane (turbulent mixture) 


5 


15 


Ethane 


3 2 


12 5 


Propane- 


2 4 


9 5 


Butane 


19 


85 


Pentane 


1 45 


7 5 


Ethylene 


3 


29 


Acetylene - 


3 




Acetylene (turbulent mixture) 


2 3 




Benzene. 


1 4 


7 


Toluene. 


1 4 


7 


Cyclohexane 


13 


8 3 


Methyl cyclohexane 


1 2 




Methyl alcohoL 


7 




Ethyl alcohol 


4 


19 


Ethyl ether._ .. . 


1 7 


26 


Benzine 


1 1 




Gasoline 


1 4 


6 


Water gas 


6 to 9 


55 to 70 


Ethylene oxide 


3.0 


80 


Acetaldehyde 


4 


57 


Furfural (125 C) 


2.0 




Acetone 


3 


11 


Acetone (turbulent mixture) 


2.5 




Methyl ethyl ketone. 


2 


12 


Methyl formate 


6 


20 


Ethyl formate 


3 5 


16 5 


Methyl acetate- 


4 1 


14 


Ethyl acetate 


2 5 


11 5 


Proovl acetate 


2 




Butyl acetate (30 C) 


1.7 




Ethyl nitrite. 


3.0 




Methyl chloride 


8 


19 


Methyl bromide ... 


13.5 


14 5 


Ethyl chloride 


4 


15 


Ethyl bromide 


7 


11 


Ethylene dichloride 


6 


16 


Dichlorethylene 


10 


13 


Vinyl chloride, 


4.0 


22.0 


Pyridine (70 C) 


1.8 


12 5 


Natural gas 


4 8 


13 5 


Illuminating gas 


5.3 


31 


Blast-furnace eras 


35 


74 









^Limits of Inflammability of Gases and Vapors, by H. F. Coward and G. W. Jones, (U. S. Bureau < 
Mines, Bulletin No. 279, 1931). 



81 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



average eye is around 50 microns all air floated material of this kind is too 
small to identify without the aid of the microscope. 

Mineral particles, such as grains of sand, bits of rock, volcanic ash, or 
fly-ash, can be transported long distances under unusual circumstances. 
Thus, the dust storms of 1935 in the Kansas district resulted in vast 
amounts of fine top soil being thrown high into the air. Solar illumination 
as far east as Boston was affected noticeably and particles as large as 40 
to 50 microns were actually carried half way across the continent before 
they settled out. In similar manner volcanic ash has been carried even 
further. It is not surprising, therefore, that fly-ash from furnace gases, 
cement dust and the like, can be carried for considerable distances and 
occasionally the engineer is confronted with the problem of removing such 
material before the air in question is suitable for use in building venti- 
lation. 

The physical properties of the particulate impurities of air are summar- 
ized conveniently in the chart of Fig. 1. 

In the case of gases the physical property which is probably of most 
importance is inflammability. The best data available at present on this 
subject are given in Table 1. 

Dust Concentrations 

It is customary to report dust concentrations as grains per 1000 cu ft 
or milligrams per cubic meter. Gas concentrations are commonly' re- 
corded as milligrams per cubic meter or as parts per million or as per 
cent by volume. Typical ranges in dust concentrations as now found in 
practical applications are given in Table 2. 

TABLE 2. DCST CONCENTRATION RANGES IN PRACTICAL APPLICATIONS** 



APPLICATION 


GRAINS PER 1000 Cn FT 


MGS PER Cu M 


Rural and suburban districts 


2 to 04 


04. rn ft fc 


Metropolitan districts 


4 to 08 


9 to 1 8 


Industrial districts 


8 to 15 


1 8 to 3 5 


Dusty factories or mines 


4 to 80 


10 to 200 


Explosive concentrations (as of flour or soft coal).. 


4000 to 8000 


10,000 to 20,000 



1 grain per 1000 cu ft = 2.3 mgs per cubic meter; 1 oz per cubic foot =* 1 gram per liter. 

The engineer frequently desires information regarding the effects of 
various concentrations of gases or dusts upon man, as the success of a 
particular installation may depend upon the maintenance of air which is 
adequately clean. At the present time there are a number of organi- 
zations working on this problem all of them publishing literature of 
various kinds. 1 References to books covering the hygienic significance, 
determination and control of dust are listed at the end of this chapter. 



m 
meat of 



f' S-P^lic Health Service; Division of Labor Standards, U. S. Depart- 
of Toronto Medical School, Canada; Saranac Laboratories, Saranac Lake 
' In ", ^^S^A **- Harvard ^ h001 of Public Health! BoS?, M .\ 
: 1 '^ the Departraents of Health and f Labor in the United States 



82 



CHAPTER 4. AIR POLLUTION 



AIR POLLUTION AND HEALTH 

The prevention of various diseases which result from exposure to 
atmospheric impurities is an engineering problem. It is important for 
the engineer to insure, by proper ventilation, suitable environments for 
working or for general living. If the equipment used is to be successful, it 
must operate automatically as in the modern air conditioned theatre or 
railroad train. 

In Table 3 are given data on permissable concentrations of various 
substances, gases and dusts, which occur in industry. The prudent 

TABLE 3. TOXICITY OF GASES AND FUMES IN PARTS PER 10,000 PARTS OF AiR a 



VAPOR OB GAS 


RAPIDLY 
FATAL 


MAXIMUM 
CONCENTRATION 

FOR FROM 

M TO 1 HOUR 


\ 

1 MAXIMUM 
CONCENTRATION 
FOR 1 HOUH 


MAXIMUM 
ALLOWABLE 
FOR PROLONGED 
EXPOSURE 


Carbon monoxide 
Carbon dioxide 


40 
800-1000 


15-20 


10 


1 


Hydrocyanic acid 


30 


\ 1 A 


'"y" 


l.< 


Ammonia 


50-100 


25 


3 


1 


Hydrochloric acid gas 


10-20 






Ko 


Chlorine....". 


10 


\s 




Koo 


Hydrofluoric acid gas._ 


2 


Mo 




3*33 


Sulphur dioxide.- 


4-5 


M-l 





s^.Q 


Hydrogen sulphide 

Carbon bisulphide. 


10-30 


5-7 
11 


2-3 

5 


1 

\4 


Phosphene 


20 


4-6 


1 2 




Arsine 


2H 




1 A 




Phosgene 


Over 34 


i/ 




Mnn 


Nitrous furnes 


2^-7i| 


1-1 H 




7Q 


Benzene 


190 




31-47 


lU-3 


Toluene and xylene 


190 




31-47 




Aniline 






1-1^ 


Kn 


Nitrobenzene 






Hoo 


i/ 

44 i\f\ 


Carbon tetrachloride 
Chloroform 


480 
250 


240 
140 


40 
50 


1 

2 


Tetrachlorethane _ 
Trichlorethylene 


73 
370 






Ho 


Methyl chloride..... 
Methyl bromide 


1500-3000 
200-400 


200-400 
20-40 


70 
10 


5-10 
2 


Lead dust. 








15 mg/cu m 


Quartz dust 








1 mg/cu m 













^Adapted from Y. Henderson and H. Haggard. (See ^oxtows Gases, 1927, and Lessotw Learned from 
Industrial Gases and Fumes, Institute of Chemistry of Great Britain and Ireland, London, 1930.) 

engineer will design equipment using these bench marks as the upper 
limits of pollution. In general it is good practice to avoid recirculation 
of air which contains originally toxic substances. Obviously there may be 
exceptions to this rule, but it is one which is generally being followed in 
current practice. 

' Bronchitis is the chief condition associated with exposure to thick dust, 
and follows upon inhalation of practically any kind of insoluble and non- 
colloidal dust. Atmospheric dust in itself cannot be blamed for causing 
tuberculosis, but it may aggravate the disease once it has started. 2 



'Physiological Response of the Peritoneal Tissue to Dusts Introduced as Foreign Bodies, by Miller 
and Sayers (U. S. Public Health Reports, 49:80, 1934). 

83 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

The sulphurous fumes and tarry matter in smoke are more dangerous 
than the carbon. In foggy weather the accumulation of these substances 
in the lower strata may be such as to cause irritation of the eyes, nose, and 
respiratory passages, leading to asthmatic breathing and bronchitis and, 
in extreme cases, to death. The Meuse Valley fog disaster will probably 
become a classic example in the history of gaseous air pollution. Re- 
leased in a rare combination of atmospheric calm and dense ^fog, it^is 
believed that sulphur dioxide and other toxic gases from the industrial 
region of the valley caused 63 sudden deaths, and injuries to several 
hundred persons. 

Carbon monoxide from automobiles and from chimney ^ gases consti- 
tutes another important source of aerial pollution in busy cities. During 
heavy traffic hours and under atmospheric conditions favorable to con- 
centration, the air of congested streets is found to contain enough CO to 
menace the health of those exposed over a period of several hours, par- 
ticularly if their activities call for deep and rapid breathing.^ In open air 
under ordinary conditions the concentration of CO in city air is insufficient 
to affect the average city dweller or pedestrian. 

Occlusion of Solar Radiation 

The loss of light, particularly the occlusion of solar ultra-violet light 
due to smoke and soot, is beginning to be recognized as a health problem 
in many industrial cities. Measurements of solar radiation in Baltimore 3 
by actinic methods show that the ultra-violet light in the country was 
50 per cent greater than in the city. In New York City 4 a loss as great as 
50 per cent in visible light was found by the photo-electric cell method. 

Recent studies 5 in Pittsburgh indicate that heavy smoke pollution is 
definitely unhealthful. Heretofore adequate proofs on this point were 
lacking. 

The aesthetic and economic objections to air pollution are so definite, 
and the effect of air-borne pollen can be shown so readily as the cause of 
hay fever and other allergic diseases, that means and expenses of pre- 
vention or elimination of this pollution are justified. 

SMOKE AND AIR POLLUTION ABATEMENT 

Successful abatement of atmospheric pollution requires the combined 
efforts of the combustion engineer, the public health officer, and the 
public itself. The complete electrification of industry and railroads, and 
the separation of industrial and residential communities would aid 
materially in the effective solution of the problem. 

In the large cities where the nuisance from smoke, dust and cinders is 
the most serious, limited areas obtain some relief by the use of district 
heating. The boilers in these plants are of large size designed and oper- 
ated to burn the fuel without smoke, and some of them are equipped with 
dust catching devices. The gases of combustion are usually discharged at 



'Effects of Atmospheric Pollution Upon Incidence of Solar Ultra-Violet Light, by J. H. Shrader, M. H. 
Coblentz and F. A. Korff (American Journal of Public Health, p. 7, Vol. 19, 1929). 

'Studies in Illumination, by J. E. Ives (U. S. Public Health Service Bulletin No. 197, 1930). 

'Pneumoconiosis in the Pittsburgh district, Based on a Study of 2,500 Post Mortem Examinations 
made in Pittsburgh Hospitals, by Schnurer et al (Journal Industrial Hygiene, 17:294, March, 1935). 

84 



CHAPTER 4. AIR POLLUTION 



a much higher level than is possible in the case of buildings that operate 
their own boiler plants. 

In general, time, temperature and turbulence are the essential require- 
ments for smokeless combustion. Anything that can be done to increase 
any one of these factors will reduce the quantity of smoke discharged. 
Especial care must be taken in hand-firing bituminous coals. (See 
Chapter 9.) 

Checker or alternate firing, in which the fuel is fired alternately on 
separate parts of the grate > maintains a higher furnace temperature and 
thereby decreases the amount of smoke. 

Coking and firing, in which the fuel is first fired close to the firing door 
and the coke pushed back into the furnace just before firing again, pro- 
duces the same effect. The volatiles as they are distilled thus have to 
pass over the hot fuel bed where they will be burned if they are mixed with 
sufficient air and are not cooled too quickly by the heat-absorbing surfaces 
of the boiler. 

Steam or compressed air jets t admitted over the fire, create turbulence 
in the furnace and bring the volatiles of the fuel more quickly into contact 
with the air required for combustion. These jets are especially helpful 
for the first few minutes after each firing. Frequent firings of small 
charges shorten the smoking period and reduce the density. Thinner 
fuel beds on the grate increase the effective combustion space in the 
furnace, supply more air for combustion, and are sometimes effective in 
reducing the smoke emitted, but care should be taken that holes are not 
formed in the fire. A lower volatile coal or a higher gravity oil always 
produces less smoke than a high volatile coal or low gravity oil used in 
the same furnace and fired in the same manner. 

The installation of more modern or better designed fuel burning equip- 
ment, or a change in the construction of the furnace, will often reduce 
smoke. The installation of a Dutch oven which will increase the furnace 
volume and raise the furnace temperature often produces satisfactory- 
results. 

In the case of new installations, the problem of smoke abatement can 
be solved by the selection of the proper fuel-burning equipment and 
furnace design for the particular fuel to be burned and by the proper 
operation of that equipment. Constant vigilance is necessary to make 
certain that the equipment is properly operated. In old installations the 
solution of the problem presents many difficulties, and a considerable 
investment in special apparatus is necessary. 

Legislative measures at the present time are largely concerned with the 
smoke discharged from the chimneys of boiler plants. Practically all of 
the ordinances limit the number of minutes in any one hour that smoke of 
a specified density, as measured by comparison with a Ringelmann Chart 
(Chapter 44), may be discharged. 

These ordinances do not cover the smoke discharged at low levels by 
automobiles, and, although they have been instrumental in reducing the 
smoke emitted by boiler plants, they have, in many instances, increased 
the output of chimney dust and cinders due to the use of more excess air 
and to greater turbulence in the furnaces. 

Legislative measures in general have not as yet covered the noxious 

85 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

gases, such as sulphur dioxide and sulphuric acid mist, which are dis- 
charged with the gases of combustion. ^ Where high sulphur coals are 
burned, these sulphur gases present a serious problem. 

DUST AND CINDERS 

The impurities in the air other than smoke come from so many sources 
that they are difficult to control. Only those which are produced in 
large quantities at a comparatively few points, such as the dust, cinders 
and fly-ash discharged to the atmosphere along with the gases of com- 
bustion from burning solid fuel, can be readily controlled. 

Dusts and cinders in flue gas may be caught by various devices on the 
market, such as fabric filters, dust traps, settling chambers, centrifugal 
separators, electrical precipitators, and gas scrubbers, described in 
Chapter 26. 

The cinder particles are usually larger in size than the dust particles; 
they are gray or black in color, and are abrasive. Being of a larger size, 
the range within which they may annoy is limited. 

The dust particles are usually extremely fine; they are light gray or 
yellow in color, and are not as abrasive as cinder particles. Being ex- 
tremely fine, they are readily distributed over a large area by air currents. 

The nuisance created by the solid particles in the air is dependent on 
the size and physical characteristics of the individual particles. The 
difficulty of catching the dust and cinder particles is principally a function 
of the size and specific gravity of the particles. 

Lower rates of combustion per square foot of grate area will reduce the 
quantity of solid matter discharged from the chimney with the gases of 
combustion. The burning of coke, coking coal, and sized coal from which 
the extremely fine coal has been removed will not as a general rule produce 
as much dust and cinders as will result from the burning of non-coking 
coals and slack coal when they are burned on a grate. 

Modern boiler installations are usually designed for high capacity per 
square foot of ground area because such designs give the lowest cost of 
construction per unit of capacity. Designs of this type discharge a 
large quantity of dust and cinders with the gases of combustion, and if 
pollution of the atmosphere is to be prevented, some type of catcher must 
be installed. 

NATURE'S DUST CATCHER 

Nature has provided means for catching solid particles in the air and 
depositing them upon the earth. A dust particle forms the nucleus for 
each rain drop and the rain picks up dust as it falls from the clouds to the 
earth. In fact, without dust in the air to form the nuclei for rain drops it 
would never rain, and the earth would be continually enveloped in a 
cloud of vapor. However, it was found in recent studies 6 that rain was 
not a good air cleaner of the material below about 0.7 micron. 



Atmospheric Pollution of American Cities for the years 1931-1933, by J. E. Ives et al (U. 5. Public 
Health Bulletin No* 224. March, 1936). 



CHAPTER 4. AIR POU.UTION 



REFERENCES 

Bulletin, Air Hygiene Foundation, Inc., Pittsburgh, Pa. 

Determination and Control of Industrial Dust, by J. J. Bloomfield and J. M. Dalla 
Valle (U. S. Public Health Bulletin, No, 217, 1935).' 

Journal of Industrial Hygiene and Toxicology, Harvard School of Public Health, 
Boston, Mass. 

Reports of the National Silicosis Conference, Washington, D. C. To be published 
by the U. S. Department of Labor. 

Saranac Symposium on Silicosis, 1937, Saranac Laboratories, Saranac, N. Y. 

Industrial Dust, by Philip Drinker and Theodore Hatch, McGraw Hill Co., N. Y. 

Noxious Gases, by Y. Henderson and H. Haggard, Chemical Catalog Co., N. Y. 

Occupation and Health, International Labour Office. 

Preventive Medicine and Hygiene, by Milton J. Rosenau, D. Appleton- Century 
Co., N. Y. 



PROBLEMS IN PRACTICE 

1 Classify the detrimental aspects of air pollution as it affects large industrial 
communities. 

Air pollution may be classified (a) medical, as it affects the physiological functions of 
people; (b) botanical, as it affects vegetation, trees, plants, shrubs and flowers; and (c) 
physical, as it affects the discoloration and deterioration of buildings, and the nuisance 
of soiled interior furnishings, clothes, merchandise, etc. 

2 Distinguish between dusts, fumes, and smokes. 

Solid particles ranging in size from 1.0 micron to 150 microns are called dusts (micron = 
Ms. ooo in.)- 

Particles resulting from sundry chemical reactions and ranging from 0.1 to 1.0 micron in 
size are called fumes. 

Carbon particles less than 0.1 micron in size which generally arise from the incomplete 
combustion of such materials as coal, oil, or tobacco are called smokes, 

3 What are some of the more important physical properties of these various 
groups of foreign bodies which are of importance in ventilation? 

In slowly moving air, dusts tend to settle out by gravity without agglomerating to form 
larger particles; fumes have the tendency to form larger particles which will settle when 
they attain the size of approximately 1.0 micron; while smokes tend to diffuse and remain 
in the air as permanent impurities. 

4 Why is atmospheric pollution an important engineering problem? 

a. Certain impurities, when present in too great concentrations, cause ill health or even 
death. 

b. High concentrations of solids occlude solar radiations. 

c. Some materials cause permanent injury to parts of buildings, as sulphur fumes corrode 
exposed metal. 

d. Extra cleaning expense is incurred in dusty localities. 

e. Internal combustion engines are damaged by abrasive dusts. 

5 How may the hazards of dust-producing industrial operations best be 
curtailed? 

By providing mechanical exhaust ventilation sufficient to keep dust concentration at a 
safe level (see Table 3) and then removing foreign bodies to reduce the pollution of out- 
side air. 

87 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

6 How may the pollution of the atmosphere he lessened? 

By compelling industrial plants to install dust catching and smoke controlling devices. 
In many cities the domestic heating plant is one of the most serious offenders, but these 
plants are too small to justify the installation of dust catchers. Public education in 
improved firing methods would be of considerable help in this field. 

7 What size particles are detrimental to health? 

While fairly large particles may enter the upper air passages, those found in the lungs 
are seldom more than 10 microns in size, and comparatively few of them are more than 
5 microns. It is agreed that particles between % and 2 microns may be harmful; some 
authorities place the upper limit at about 5 microns, and some incline to extend the 
lower limit to 0.1 of a micron. 

8 Is the shape of the particle of any significance? 

Hard particles with sharp corners or edges have a cutting effect on the delicate mucous 
membranes of the upper respiratory tract which may lower the resistance of the nose and 
throat to acute infections. This is aggravated by the irritating effects of some chemical 
compounds which may be taken in with the air and which act to reduce resistance. 

9 What are the principal meteorological effects of smoke and dust? 

a. The reduction in the amount of light received. Measurements have shown that 
visible light may be as much as 50 per cent less intense in a smoky section of a city than 
in a section that is free from smoke. Ultra-violet light is reduced as much or more, and 
in some cases is cut out entirely for a time. 

6. Smoke and dust aid in the formation and prolongation of fogs. City fogs accumulate 
smoke and become darker in color and very objectionable. The sun requires a longer 
time to disperse them, and when the water is evaporated, there is a rain of smoke and 
soot particles that have been entrained. 

10 Why has not smoke abatement been more effective? 

Because communities have not been made sufficiently aware of the possibilities of 
burning high volatile fuels smokelessly and of separating cinder and ash from the stack 
gases to a degree that will prevent a nuisance. 

11 Is the abatement of dust and cinders important? 

Yes. Only a small percentage of the solid emission from stacks is smoke, in the accepted 
popular sense; the remainder is fly-ash and cinders. While black smoke is disagreeable 
and its tarry matter and carbon particles soil anything with which they come in contact, 
the cinders and some of the ash are hard and destructive. They also, together with 
dusts from industrial processes, make up the irritating, air-borne solids that are breathed 
by individuals not working in a dusty mill or factory. 

12 Are air-borne impurities causative factors in hay fever, bronchial asthma, 
and allergic disorders? 

Yes. Recent medical investigations indicate that 90 per cent of seasonal hay fever and 
40 per cent of bronchial asthma are caused by air-borne pollens, tree dusts, and other 
allergic irritants. 

13 Name some essential requirements for the smokeless combustion of fuels. 

Time, temperature, and turbulence. A study of these factors is usually of value in 
overcoming a smoke nuisance. 

14 What is the Ringelmann Chart Method of comparing smoke densities? 

See Chapter 44. The Ringelmann Chart consists of four cards ruled with lines having 
different degrees of blackness. These cards, together with a white card and a black one, 
are^hung in a horizontal row 50 ft from the observer. At this distance the lines become 
invisible and the cards appear to be different shades of gray, ranging from white to black. 
The observer, by matching the cards against the shades of smoke coming from a stack, is 
able to estimate the blackness of the smoke as compared with the chart. 

88 



Chapter 5 

HEAT TRANSMISSION COEFFICIENTS 
AND TABLES 

Methods o Heat Transfer, Coefficients, Conductivity of 
Homogeneous Materials, Surface Conductance Coefficients, 
Air Space Conductance, Practical Coefficients, Table of Con- 
ductivities and Conductances, Tables of Over- all Coefficients 
of Heat Transfer for Typical Building Construction, Combined 
Coefficients of Transmission 

IN order to maintain comfortable living temperatures within a building 
it is necessary to supply heat at the same rate that it is lost from the 
building. The loss of heat occurs in two ways, by direct transmission 
through the various parts of the structure and by air leakage or filtration 
between the inside and outside of the building. The purpose of this 
chapter is to show methods of calculation and to give practical trans- 
mission coefficients which may be applied to various structures to deter- 
mine the heat loss by direct transmission. The amount lost by air 
nitration is determined by different methods, as outlined in Chapter 6, 
and must be added to that lost by direct transmission to obtain the total 
heating plant requirements. 

METHODS OF HEAT TRANSFER 

Heat transmission between the air on the two sides of a structure takes 
place by three methods, namely, radiation, convection and conduction. 
In a simple wall built up of two layers of homogeneous materials separated 
to give an air space between them, heat will be received from the high 
temperature surface by radiation, convection and conduction. It will 
then be conducted through the homogeneous interior section by con- 
duction and carried across to the opposite surface of the air space by 
radiation, conduction and convection. From here it will be carried by 
conduction through to the outer surface and leave the outer surface by 
radiation, convection and conduction. The process of heat transfer 
through a built-up wall section is complicated in theory, but in practice 
it is simplified by dividing a wall into its component parts and considering 
the transmission through each part separately. Thus the average wall 
may be divided into external surfaces, homogeneous materials and interior 
air spaces. Practical heat transmission coefficients may be derived which 
will give the total heat transferred by radiation, conduction and convec- 
tion through any of these component parts and if the selection and method 
of applying these individual coefficients is thoroughly understood it is 
usually a comparatively simple matter to calculate the over-all heat 
transmission coefficient for any combination of materials. 

89 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



HEAT TRANSFER COEFFICIENTS 

The symbols representing the various coefficients of heat transmission 
and their definitions are as follows : 

U = thermal^ transmittance or over-all coefficient of heat transmission ; the amount of 
heat expressed in Btu transmitted in one hour per square foot of the wall, floor, roof or 
ceiling for a difference in temperature of 1 deg F between the air on the inside and that 
on the outside of the wall, floor, roof or ceiling. 

k = thermal conductivity; the amount of heat expressed in Btu transmitted in one 
hour through 1 sq ft of a homogeneous material 1 in. thick for a difference in temperature 
of 1 deg F between the two surfaces of the material. The conductivity of any material 
depends on the structure of the material and its density. Heavy or dense materials, the 
weight of which per cubic foot is high, usually transmit more heat than light or less dense 
materials, the weight of which per cubic foot is low. 

C = thermal conductance; the amount of heat expressed in Btu transmitted in one 
hour through 1 sq ft of a non-homogeneous material for the thickness or type under 
consideration for a difference in temperature of 1 deg F between the two surfaces of the 
material. Conductance is usually used to designate the heat transmitted through such 
heterogeneous materials as plaster board and hollow clay tile. 

/ = film or surface conductance; the amount of heat expressed in Btu transmitted by 
radiation, conduction and convection from a surface to the air surrounding it, or vice 
versa, in one hour per square foot of the surface for a difference in temperature of 1 deg F 
between the surface and the surrounding air. To differentiate between inside and outside 
wall (or floor, roof or ceiling) surfaces, fi is used to designate the inside film or surface 
conductance and / the outside film or surface conductance. 

a thermal conductance of an air space; the amount of heat expressed in Btu trans- 
mitted by radiation, conduction and convection in one hour through an area of 1 sq ft of 
an air space for a temperature difference of 1 deg F. The conductance of an air space 
depends on the mean absolute temperature, the width, the position and the character of 
the materials enclosing it. 

R resistance or resistivity which is the reciprocal of transmission, conductance, 
or conductivity, i.e.: 

-jj- - over-all or air-to-air resistance. 
-T~ = internal resistivity. 

TT internal resistance, 
c/ 

-j- film or surface resistance. 

1 
= air-space resistance. 

As an example in the application of these coefficients assume a wall 
with over-all coefficient U. Then, 

H = AU(t-to) (1) 

where 

H = Btu per hour transmitted through the material of the wall, glass, roof or 
floor. 

A * area in square feet of wall, glass, roof, floor, or material, taken from building 
plans or actually measured. (Use the net inside or heated surface dimensions 
in all cases.) 

- k = temperature difference between inside and outside air, in which t must always 
be taken at the proper level. Note that t may not be the breathing-line 



90 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 

If the heat transfer between the air and the inside surface of the wall 
is being considered, then, 

H = A fi (t - h) f2) 

where 

fi = inside surface conductance. 

t and h = the temperatures of the inside air and the inside surface of the wall re- 
spectively. 

In practice it is usually the over-all heat transmission coefficient that is 
required. This may be determined by a test of the complete wall, or 
it may be obtained from the individual coefficients by calculation. The 
simplest method of combining the coefficients for the individual parts of 
the wall is to use the reciprocals of the coefficients and treat them as 
resistance units. The total over-all resistance of a wall is equal numeri- 
cally to the sum of the resistances of the various parts, and the reciprocal 
of the over-all resistance is likewise the over-all heat transmission coef- 
ficient of the wall. For a wall built up of a single homogeneous material 
of conductivity k and x inches thick the over-all resistance, 



If the coefficients /i,/ and k, together with the thickness of the material 
x are known, the over-all coefficient U may be readily calculated as the 
reciprocal of the total heat resistance. 

For a compound wall built up of three homogeneous materials having 
conductivities AI, & 2 and k s and thicknesses xi, x z and x$ respectively, and 
laid together without air spaces, the total resistance, 

l=! + i + t+t + i 

For a wall with air space construction consisting of two homogeneous 
materials of thicknesses Xi and x 2 and conductivities ki and k z , respectively, 
separated to form an air space of conductance a, the over-all resistance, 

-L - 4- -5- 4-+ -5-4- 1 ' m 

U ' fi + ft, + a + k, + 7T 5 

Likewise any combination of homogeneous materials and air spaces can 
be put into the wall and the over-all resistance of the combination may be 
calculated by adding the resistances of the individual sections of the wall. 
In certain special forms of construction such as tile with irregular air 
spaces it is necessary to consider the conductance C of the unit as built 
instead of the unit conductivity k, and the resistance of the section is 

equal to -pr. The method of calculating the over-all heat transmission 
o 

coefficient for a given wall is comparatively simple, but the selection of 
the proper coefficients is often complicated. In some cases the construc- 
tion of the wall is such that the substituting of coefficients in the accepted 
formula will give erroneous results. This is the case with irregular cored 

91 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

out air spaces in concrete and tile blocks, and walls in which there are 
parallel paths for heat flow through materials having different heat 
resistances. In such cases it is necessary to resort to test methods to 
check the calculations, and in practically all cases it has been necessary 
to determine fundamental coefficients by test methods. 

Conductivity of Homogeneous Materials 

The thermal conductivity of homogeneous materials is affected by 
several factors. Among these are the density of the material, the amount 
of moisture present, the mean temperature at which the coefficient is 
determined, and for fiberous materials the arrangement of fiber in the 
material. There are many fiberous materials used in building construc- 
tion and considered as homogeneous for the purpose of calculation, 
whereas they are not really homogeneous but are merely considered so as a 
matter of convenience. In general, the thermal conductivity of a material 
increases directly with the density of the material, increases with the 
amount of moisture present, and increases with the mean temperature at 
which the coefficient is determined. The rate of increase for these various 
factors is not the same for all materials, and in assigning proper coef- 
ficients one should make certain that they apply for the conditions under 
which the material is to be used in a wall. Failure to do this may result 
in serious errors in the final coefficients. 

Surface Conductance Coefficients 

Heat is transmitted to or from the surface of a wall by a combination 
of radiation, convection and conduction. The coefficient will be effected 
by any factor which has an influence on any one of these three methods of 
transfer. The amount of heat by radiation is controlled by the character 
of the surface and the temperature difference between it and the sur- 
rounding objects. The amount of heat by conduction and convection is 
controlled largely by the roughness of the surface, by the air movement 
over the surface and by the temperature difference between the air and 
the surface. Because of these variables the surface coefficients may be 
subject to wide fluctuations for different materials and different con- 
ditions. The inside and outside coefficients jfi and/ are in general affected 
to the same extent by these various factors and test coefficients deter- 
mined for inside surfaces will apply equally well to outside surfaces under 
like conditions. Values for /i in still and moving air at different mean 
temperatures have been determined for various building materials at the 
University of Minnesota under a cooperative agreement with the Society. 1 

The relation obtained between surface conductances for different 
materials at mean temperatures of 20 F is shown in Fig. 1. These values 
were obtained with air flow parallel to the surface and from other tests in 
which the angle of incident between the direction of air flow and the 
surface was varied from zero to 90 deg it would appear that these values 
might be lowered approximately 15 per cent for average conditions. 
While for average building materials there is a difference due to mean 
temperature, the greatest variation in these coefficients is caused by the 
character of the surface and the wind velocity. If other surfaces, such as 

'Surface Conductances as Affected by Air Velocity, Temperature and Character of Surface, by F. B. 
Rowley, A. B. Algren and J. L. Blackshaw (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 429). 

92 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 

aluminum foil with low emissivity coefficients were substituted, a large 
part of the radiant heat would be eliminated. This would reduce the 
total coefficient for all wind velocities by about 0.7 Btu and would make 
but very little difference for the higher wind velocities. In many cases in 
building construction the heat resistance of the internal parts of the wall 
is high as compared with the surface resistance and the surface factors 
become of small importance. In other cases such as single glass windows 
the surface resistances constitute practically the entire resistance of the 
structure^ and therefore become important factors. Due to the wide 
variation in surface coefficients for different conditions their selection for 




15 20 25 

AIR VELOCITY, M. P. H. 

FIG. 1. CURVES SHOWING RELATION BETWEEN SURFACE CONDUCTANCES FOR 
DIFFERENT SURFACES AT 20 F MEAN TEMPERATURE 

a practical building becomes a matter of judgment. In calculating the 
over-all coefficients for the walls of Tables 3 to 12, 1.65 has been selected 
as an average inside coefficient and 6.0 as an average outside coefficient 
for a 15-mile wind velocity. In special cases where surface coefficients 
become important factors in the over-all rate of heat transfer more 
selective coefficients may be required, 

Air Space Conductance 

Heat is conducted across an air space by a combination of radiation, 
conduction and convection. The amount of heat by radiation is governed 
largely by the nature of the surface and the temperature difference 
between the boundary surfaces of the air space. Conduction and con- 

93 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

vection are controlled largely by the width and shape of the air space and 
the roughness of the boundary surfaces. The thermal resistances of air 
spaces bounded by extended parallel surfaces perpendicular to the 
direction of heat flow and at different mean temperatures have been 
determined for average building materials at the^ University of Minnesota 
in a cooperative research program with the Society. 

The values given in Table 1 show the results of this study and apply to 
air spaces bounded by such materials as paper, wood, plaster, etc., 
having emissivity coefficients of from 0.9 to 0.95. The conductivity 
coefficients decrease with air space width until a width of about % in. has 
been reached, after which the width has but very little effect. In these 

TABLE 1. CONDUCTANCES OF AIR SPACES a AT VARIOUS MEAN TEMPERATURES 



MIAN 



COITOUCTANCZS or AIR SPACES FOR VARIOUS WIDTHS IN INCHES 



TBMP 
DBG FAHR 


0.128 


0.250 


0.364 


0.493 


0.713 


1.00 


1.500 


20 


2.300 


1.370 


1.180 


1.100 


1.040 


1.030 


1.022 


30 


2.385 


1.425 


1.234 


1.148 


1.080 


1.070 


1.065 


40 


2.470 


1.480 


1.288 


1.193 


1.125 


1.112 


1.105 


50 


2.560 


1.535 


1.340 


1.242 


1.168 


1.152 


1.149 


60 


2.650 


1.590 


1.390 


1.295 


1.210 


1.195 


1.188 


70 


2.730 


1.648 


1.440 


1.340 


1.250 


1.240 


1.228 


80 


2.819 


1.702 


1.492 


1.390 


1.295 


1.280 


1.270 


90 


2.908 


1.757 


1.547 


1.433 


1.340 


1.320 


1.310 


100 


2.990 


1.813 


1.600 


1.486 


1.380 


1.362 


1.350 


110 


3.078 


1.870 


1.650 


1.534 


1.425 


1.402 


1.392 


120 


3.167 


1.928 


1.700 


1.580 


1.467 


1.445 


1.435 


130 


3.250 


1.980 


1.750 


1.630 


1.510 


1.485 


1.475 


140 


3.340 


2.035 


1.800 


1.680 


1.550 


1.530 


1.519 


150 


3.425 


2.090 


1.852 


1.728 


1.592 


1.569 


1.559 



^Thermal Resistance of Air Spaces by F. B. Rowley and A. B. Algren (A.S.H.V.E. TRANSACTIONS, 
Vol. 35, 1929, p. 165). 

coefficients radiation is a large factor, and if surfaces with low emissivity 
coefficients are substituted for ordinary building materials the total 
amount of radiant heat will be reduced. The reduction in radiant heat 
caused by the low emissivity surface is independent of width of air space. 
Air spaces properly formed in combination with metallic surfaces such as 
aluminum foil, coated sheet steel, and other materials having a reflective 
surface, possess heat repelling characteristics. Values of air spaces 
lined with aluminum foil on one or both sides for widths of % in. and % in. 
are shown in Table 2 of conductivities. A low emissivity coefficient is 
dependent on the permanency of the reflective surface. If a bright clean 
surface is covered with a thin layer of corrosive material its reflectivity is 
appreciably reduced 2 . 

In comparing the conductance coefficients for air spaces with and with- 
out bright metallic surface lining it should be noted that the reduction in 
heat transfer is substantially as great when one surface is lined as it is 
when both surfaces are lined. The reason for this is that practically 
95 per cent of the total radiant heat is intercepted by one surface lining 



^Aluminum Foil Insulation (National Bureau of Standards Letter Circular No. LC465. June, 1936). 

94 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 

and there is but a small amount left to be stopped by the second surface 
lining. The effect of any low emissivity surface in 'stopping the trans- 
mission of radiant heat is the same regardless of whether it is on the high 
or low temperature side of the air space. For materials such as aluminum 
paint or bronze paint which stop only a small percentage of radiant heat 
there is a greater percentage of gain by addition of a second surface lining. 

PRACTICAL COEFFICIENTS 

For practical purposes it is necessary to have average coefficients that 
may be applied to various materials and types of construction without 
the necessity of making tests on the individual material or combination of 
materials. In Table 2 coefficients are given for a group of materials which 
have been selected from various sources. Wherever possible the proper- 
ties of material and conditions of tests are given. However, in selecting 
and applying these values to any construction a reasonable amount of 
caution is necessary; variations will be found in the coefficients for the 
same materials, which may be partly due to different test methods used, 
but which are largely due to variations in materials. The recommended 
coefficients which have been used for the calculation of over-all coefficients 
as given in Tables 3 to 12 are marked by an asterisk. 

It should be recognized in these tables of calculated coefficients that 
space limitations will not permit the inclusion of all the combinations of 
materials that are used in building construction and the varied applications 
of insulating materials to these constructions. Typical examples are given 
of combinations frequently used, but any special construction not given in 
Tables 3 to 12 can generally be computed by using the conductivity values 
given in Table 2 and the fundamental heat transfer formulae. For 
example, the tabulation of all of the values for multiple layers of insulating 
materials would present extensive and detailed problems of calculations 
for the varied application combinations, but the engineer having the 
fundamental conductivity values can quickly obtain the proper coefficients. 

Attention is called to the fact that the conductivity values per inch of 
thickness do not afford a true basis for comparison between insulating 
materials as applied, although they are frequently used for that purpose. 
The value of an insulating material is measured in terms of its heat 
resistance, which not only depends upon the thermal conductivity coef- 
ficient per inch but also upon the thickness as installed and the manner, of 
installation. For instance the material having a coefficient of 0.50 and 
1 in. thick is equal in value to a material having a coefficient of 0.25 and 
a thickness of J^ in. Certain types of blanket installations are designed 
to be installed between the studs of a frame building in such manner as to 
give two air spaces. In order to get the full value of such materials they 
should be so installed that each air space is approximately 1 in. or more 
in thickness and the air spaces should be sealed at the top and bottom to 
prevent the circulation of air from one space to the other. Another 
common error in installing such a material is to nail the blanket on the 
outside of the studs underneath the sheathing, in which case one air 
space is lost and also the thickness of the insulating material is materially 
reduced at the studs. There are certain other types of insulation which 
are very porous, allowing air circulation within the material if not 

95 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

properly installed. The architect or engineer must carefully evaluate the 
economic considerations involved in the selection of an insulating material 
as adapted to various building constructions. Lack of good judgment in 
the intelligent choice of an insulating material, or its improper installation, 
frequently represents the difference between good or unsatisfactory 
results. Refer to Chapter 7 for a discussion of wall condensation. 

Computed Transmission Coefficients 

Computed heat transmission coefficients of many common types of 
building construction are given in Tables 3 to 13, inclusive, each con- 
struction being identified by a serial number. For example, the coefficient 
of transmission (IT) of an 8-in. brick wall and J^ in. of plaster is 0.46, and 
the number assigned to a wall of this construction is 1-B, Table 3. 

Example L Calculate the coefficient of transmission (IT) of an 8-in. brick wall with 
J in. of plaster applied directly to the interior surface, based on an outside wind exposure 
of 15 mph. It is assumed that the outside course is of hard (high density) brick having a 
conductivity of 9.20, and that the inside course is of common (low density) brick having 
a conductivity of 5.0, the thicknesses each being 4 in. The conductivity of the plaster is 
assumed to be 3.3, and the inside and outside surface coefficients are assumed to average 
1.65 and 6.00, respectively, for still air and a 15 mph wind velocity. 

Solution, k (hard high density brick) - 9.20; x = 40 in.; k (common low density 
brick) = 5.0; x 4.0 in.; k (plaster) = 3.3; * = M in.;/i = 1.65;/ - 6.0. Therefore, 



6.0 T 9.20 ^ 5.0 ~*~ 3.3 "*" 1.65 

^ 1 

0.167 + 0.435 -i- 0.80 + 0.152 + 0.606 

0.46 Btu per hour per square foot per degree Fahrenheit difference in tempera- 
ture between the air on the two sides. 

The coefficients in the tables were determined by calculations similar 
to those shown in Example 1, using Fundamental Formulae 3, 4 and 5 
and the values of k (or C),/i, / and a indicated in Table 2 by asterisks. 
In computing heat transmission coefficients of floors laid directly on the 
ground (Table 10), only one surface coefficient (/i) is used. For example, 
the value of U for a 1-in. yellow pine floor (actual thickness, 25/32 in.) 
placed directly on 6-in. concrete on the ground, is determined as follows : 

1 
U = ~~; :rir: = 0.48 Btu per hour per square foot per degree difference 

I , U. fol , O.U 

1.65 " 0.80 12.62 
in temperature between the ground and the air immediately above the floor. 

Rigid insulation refers to the so-called board form which may be used 
structurally, such as for sheathing. Flexible insulation refers to the 
blankets, quilts or semi-rigid types of insulation. 

Actual thicknesses of lumber are used in the computations rather than 
nominal thicknesses. The computations for wood shingle roofs applied 
over wood stripping are based on 1 by 4 in. wood strips, spaced 2 in. apart. 
Since no reliable figures are available concerning the conductivity of 
Spanish and French clay roofing tile, of which there are many varieties, 
the figures for such types of roofs were taken the same as for slate roofs, as 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



TABLE 2. CONDUCTIVITIES (k) AND CONDUCTANCES (C) OF BUILDING 
MATERIALS AND INSULATORS** 

The coefficients are expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness, 
unless otherwise indicated. 



Material 


Description 


DENSITY 
(La PER Cu FT) 


MEAN TEMP. 
(DKG FAHR) 


CoNDDcrivrrr (K) 

OR 

CONDUCTANCE (C') 


~l- _,jo 

> 8 

5 3 


| 
<J 


Cement 


Fine 
Aggre- 

0-No. 4 


Coarse 
*gj" Slump 
No.4-H 


Per 
Cent 
Voids 


SAND AND GRAVEL, 

CONCRETE 


1 
1 


2.00 
2.75 
3.50 
2.00 
2.00 
2.75 
2.75 
3.50 
3.50 


2.75 
4.50 
5.50 
2.75 
2.75 
4.50 
4.50 
5.50 
5.50 




8 

1 


11.5 
10.9 
11.2 
13,9 
13.9 
14.6 
14.6 
14.7 
14.7 


144.7 
145.7 
144.5 
142.5 
142.5 
141.1 
141.1 
139.2 
139.2 

142.3 


75.06 
74.77 
75.00 
75.50 
74.74 
73.30 
74.89 
74.50 
75.15 


13.10 
12.90 
13.20 
12.10 
12.40 
12.40 
12.10 
12.85 
12.50 

12.62* 


0.08 
0.08 
0.08 
0.08 
0.08 
0.08 
0.08 
0.08 
0.08 


1 

4) 
4) 
4) 

4) 
4) 

4) 
4) 
4) 

t! 

(4) 


Avg. Value for Sand and Gravel Concrete 


LlMBSTONE CONCBETB 


1 
1 
1 
1 

1 
1 


2.00 
2.75 
3.50 
2.00 
2.75 
3.50 


2.75 
4.50 
5.50 
2.75 
4.50 
5.50 





3 

3 


16.6 
15.4 
16.3 
20.9 
23.4 
23.4 


135.3 
137.8 
136.4 
130.1 
126.0 
127.3 

132.15 


74.87 
75.18 
74.75 
74.85 
74.45 
75.26 


11.20 
12.00 
11.50 
10.50 
10.00 
9.79 

10.83 


1 0.09 
0.08 
0.09 
0.10 
0.10 
0.10 


Avg. Value for Limestone Co 


ncfftte 










CINDBR CONCRETE 


1 
1 
1 

1 
1 

1 


2.00 
2.75 
3.50 
2.00 
2.75 
3.50 


2.75 
4.50 
5.50 
2.75 
4.50 
5.50 





3 
3 
3 


18.2 
19.9 
21.4 
22.8 
26.0 
24.4 


103.6 
98.7 
92.0 
101.4 
94.0 
94.4 

97.35 


75.26 
75.71 
75.72 
74.95 
75.20 
75.55 


4.63 
4.30 
3.73 
4.89 
4.38 
4.24 

4.86 


0.22 
0.23 
0.27 
0.20 
0.23 
0.24 


4) 

I 

4) 
4) 


Avg. Value for Cinder Concrt 


>te 










HATDITE ,. 


1 
1 
1 
1 
1 
1 
1 


2.00 
2.75 
3.50 
2.00 
2.75 
2.75 
3.50 


2.75 
4.50 
5.50 
2.75 
4.50 
4.50 
5.50 






4 
4 
4 
4 


18.0 
19.8 
21.8 
21.2 
22.2 
22.2 
23.9 


80.7 
75,0 
71.7 
78,8 
72.4 
72.4 
71.0 

74.57 


74.82 
75.75 
74.82 
74.76 
75.39 
75.49 
75.46 


4.15 
3.78 
3.67 
4.38 
3.89 
3.86 
4.00 

3.96 


0.25 
0.26 
0.27 
0.23 
0.26 
0.26 
0.25 


4) 
4) 

3 
3 

4) 


Avg. Value f or Haydite , 



AUTHORITIES: 

J U. S. Bureau of Standards, tests based on samples submitted by manufacturers. 

'A. C. Willard, L. C. Lichty, and L. A. Harding, tests conducted at the University of Illinois. 

*J. C. Peebles, tests conducted at Armour Institute of Technology, based on samples submitted by 
manufacturers. 

*F. B. Rowley, tests conducted at the University of Minnesota. 

5 A.S.H.V.E. Research Laboratory. 

E. A. Allcut, tests conducted at the University of Toronto. 

'Lees and Charlton. 

8 G. B. Wilkes, tests conducted at the Massachusetts Institute of Technology. 

*Recommended conductivities and conductances for computing heat transmission coefficients. 

tFor thickness stated or used on construction, not per 1-in. thickness. 

For additional conductivity data see Chapters 3 and 15, 1937 A.S.R.E. Data Book. 

k lf outside surface of block is painted with an impervious coat of paint, add 0.07 to resistance for sand 
and gravel blocks. Add 0.18 to resistance for cinder blocks. Add 0.17 to resistance for haydite blocks. 

"Recommended value. See Heating, Ventilating and Air Conditioning, by Harding and Willard, revised 
edition, 1932. 

d See A.S.H.V.E. Research Paper, Conductivity of Concrete, by F. C. Houghten and Carl Gutberlet 
(A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 47). 

<The 6-in., 8-in. t and 10-in. hollow tile figures are based on two cells in the direction of heat now. The 
12-in. hollow tile is based on three cells in the direction of heat flow. The 16-in. hollow tile consists of one 
10-in. and one 6-in. tile, each having two cells in the direction of heat flow. 

"Roofing, 0.15-in.* thick (1.34 Ib per SQ ft), covered with gravel (0.83 Ib per sq ft), combined thickness 
assumed 0.25. 

A Surface values were obtained on vertical surfaces and varying with the temperature differences. A 
foil lined air space in a horizontal position will have a coefficient roughly three times greater if the heat 
flow is upward rather than downward. 

97 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 2. CONDUCTIVITIES \k) AND CONDUCTANCES (C) OF BUILDING 
MATERIALS AND INSULATORS Continued 

The coeficients are expressed in Biu per hour per square foot per degree Fahrenheit per 1 in. thickness 
unless otherwise indicated. 





Material 




Description 


DENSITY 
(LB PER Cu FT) 


IMEAN TEMP. 
(DEQ FAHR) 


CONDUCTIVITY (fc) 

OR 

CONDUCTANCE (C) 


g g 

hi 


EH 
1 


Fine Coarse p er 
O-No. 4 No. 4-J^ , 01 


EXPANDED BUBNED CLAY 1 , 8.00 18.4 
STBAJC TREATED LIMESTONE SLAG- j 1 ; 7.00 27.1 
PUIIICI; MTNED TN CAT.TF 1 ; 8.00 26.5 


57.9 
74.6 
65.0 


75.57 
74.49 
74.68 


2.28 
2.27 
2.42 


0.44 
0.44 
0.41 


(4) 
(4) 
(4) 


BY-PHODUCT OF MANUFACTURE ' 1 ,8.00 Modulus 25.5 
OF PHOSPHATES ' 1 1 8.00 3.75 21.1 


86.6 
91.1 


74.62 
74.43 


3.19 
3.42 


0.31 
0.29 


(4) 
(4) 


HATDIT 






1 j 8.50 21.8 
1 i 8.50 21.8 


67.1 
67.1 


75.89 
74.60 


2.89 
2.815 


0.35 
0.34 


(4) 
(4) 






f l 16 l-w* CM cwwTfft ttocn 


Sand and v 1 te 


126.4 


40 

40"~ 
40 
40 

40"' 

40 
40 
40 
40 


0.900 

1.000 
0.560 
0.856 
0.577 
0.600 
0.390 
0.250 
0.266 
0.495 
0.206 


\ 

F 

* 

,* 

* 
* 
* 


l.ll 

1.00 
1.79 
1.17 
1.73 
1.66 
2.56 
4.00 
3.76 
2.02 
4.85 


(4) 

2 

4) 

ti 

4) 

t! 
i! 


Sand and gravel aggregate used for calcu- 
lations _ 


a- ] 


^j ^JL* 


At 


Cores filled with 5. 14 Ib density cork 
Crushed limestone aggregate 


134.3 
86.2 


Cinder aggregate ,_ , 


Cinder aggregate used for calculations ~ 


Cores filled with 69.7 Ib density cinders 
Cores filled with 5 . 12 Ib density cork- 




J5J- 




Cores filled with U.2 Ib density rock wool 
TIftydite aggregate 


67.7 


Cores MeJTwith 5.06 Ib density cork 


8>12 


,,63.c*~ <***> 


*>', 


Sand and gravel aggregate.. _ 
Sand and gravel aggregate used for calcu- 
lations i , . - 


124.9 


40 


0.777f 

O.SOOf* 
0.531f* 
0.237f* 
0.468f 
0.168f* 


1.29 

1,88 
4.22 
2.13 
5.94 


(4) 
4) 

tl 

4) 
4) 


->} 

L 


Or 
1 
x_S*- ' 


If 

T, 


Cinder aggregate ~~-..-~..~ _...__.. 
Cores filled with 5.24 Ib density cork. 


86.2 
__, 


40 
40 
40 
40 


Cores filledwith 5 .6 Ib density cork. 


.5f -f 


-.jvrf 


Cinder aggregate- 

Double waU with 1 in. air space between 
1 in. space filled with 9.97 ID density rock wool 


100.0 
100.0 
100.0 


40 
40 
40 


l.OOOf 
0.358f 
0.204f 


1.00 
2.70 
4.90 


4) 
4) 
4) 

(4) 


!> 


j run r~ 


= > i 


, .s, , 




,. n *_ 




5x8x12 block sand and gravel aggregate. 


133.7 


40 


0.380f 


2.6.? 


JJ'^^E 


gtjij 






iin^ 1 ^ 


-rH* 


1 










-,*-*-, -" 




5x8x12 block sand and gravel aggregate*.. 


134.0 


40 


0.947f 


1.06 


(4) 




Ti! 

ilT 


m 


u 





For notes see Page 97. 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



TABLE 2. 



CONDUCTIVITIES (k) AND CONDUCTANCES (C) OF BUILDING 
MATERIALS AND INSULATORS Continued 



The coefficients are expressed in Btu per hour per square jopt per degree Fahrenheit per 1 in. thickness, 
unless otherwise indicated. 



Material 


Description 


DENSITY 
(LB PER Cu FT) 


II 
li 


CONDUCTIVITY (Jt) 

OR 

CONDUCTANCE (C') 


-M'rf* -T'O 

T.T 

3 


t 

-aj 


MASONRY MATERIALS 


Low density 






5.00* 
9.20* 
5.00* 
12.00* 
ll.SSfo 1 
16.36 
1.06 
1.44 
1.80 
2.18 

1.66* 

3.98 
12.50* 
12.00* 

i.oot* 

0.64f* 
0.60f* 
0.58f* 
0.40f* 
0.31t* 

i.oot 

0.60t 
0.47t 
0.46t* 
1.66 
2.96 
12.00* 


0.20 
0.11 
0.20 
0.08 

0.94 
0.69 
0.56 
0.46 

0.60 

0.25 
0.08 
0.08 
1.00 
1.57 
1.67 
1.72 
2.50 
3.23 
1.00 
1.67 
2.13 
2.18 
0.60 
0.34 
0.08 


(5 

1 

(3) 
(3) 
(3) 

(4) 
(3) 




High density 




75 
75 
75 
75 

74 
70 


Damp or wet 


CEMENT MORTAR. 
CONCRETE 

STONE 

SrrjCCO _ _ 

TILE. 


Typical . . - 


40.0 
50.0 
60.0 
70.0 

51.2 
101.0 


Various ages and mixes'' . 
Cellular 


Cellular_ 
Cellular .. 


Cellular 

Typical fiber gypsum, 87.5% gypsum and 
12.5% wood chips 
Special concrete made with an aggregate of 
hardened clay~l-2~3 mix_-,..~ 
Typical- . 


Typical .. 





Typical hollow clay 4 in.) 


TILE OR TBHRAZZO 


Typical hollow clay 6 in.)* 








Typical hollow clay 8 in.)* _ - ..- 


Typical hollow clay 10 in.)" - 






Typical hollow clay 12 in,)* 
Typical hollow clay 16 in,)* 





no" 

100 

105 

"70" 

76 


(2) 

8 
@ 


Hollow clay (2 in.)H-in. plaster both sides 
Hollow clay (4 in.) J^-in. plaster both sides 
Hollow clay (6 in.) l /fcaa. plaster both sides. 
Hollow gypsum (4 in.) _ 
Solid gypsum _ 
Solid gypsuin_..- - 
Typical flooring- 


120.0 
127.0 
124.3 

YlT 
75.6 


INSULATION BLANKET 
OR FLEXIBLE TYPES 

FlBlR- 


Typical 


3.62 
4.60 
3.40 
4.90 

5.76 

7.70 
11.00 
1.00 
6.70 

12.1 


70 
90 
90 
90 

71 

71 
75 
90 
75 

75 


0.27* 

0.25 
0.26 
0.25 
0.28 

0.26 

0.28 
0.25 
0.24 
0.25 

0.40t 


3.70 

4.00 
3.85 
4.00 
3.57 

3.85 

3.57 
4.00 
4.17 
4.00 

2.50 


(3) 
1) 
1) 
(1) 

(3) 
(3) 

@ 

(3) 
(4) 




Chemically treated wood fibers held between 
layers of strong pjiper/.,.. _ -.- - - 


Eel grass between strong paper/ 

Flax fibers between strong paper/. 
Chemically treated hog hair between kraf t 
paper/ 


Chemically treated hog hair between kraft 
paper and asbestos pap?! 1 / - - 


Hair felt between layers "of paper/ 


Kapok between burlap or paper/ 
Jute fiber/ ... . 


Ground paper between two layers, each %-in. 
thick maae up of two layers of kraft paper 
(sample %-in. thick) 


INSULATION SEMI- 
RIGID TYPE 

FlBBR 


Felted cattle h^>/ 


13.00 
11.00 
12.10 
13.60 
7.80 
6.30 
6.10 
6.70 
10.00 
11.00 


90 
90 
70 
90 
90 
90 
90 
75 
90 
70 


0.26 
0.26 
0.30 
0.32 
0.28 
0.27 
0.26 
0.25 
0.37 
0.26 


3.84 
3.84 
3.33 
3.12 
3.57 
3.70 
3.85 
4.00 
2.70 
3.84 


1) 
1) 

1) 

i 

i) 

3) 




K UK 


Flax/ . - - 


Flax and rye/ 
Felted hair and asbestos/ - 


75% hair and 25% jute/ 


50% hair and 50% jute/ .. _ 


j u te/ "' ._ ._ 


Felted jute and asbestos/ - . 


Compressed peat moss 


INSULATIONLOOSE 
FILL OR BAT TYPE 
"BY** 


Made from ceiba fibers/ 

a a ^ 


1.90 
1.60 


75 
75 


0.23 
0.24 


4.35 
4.17 


(3) 
(3) 





For notes see page 97. 



99 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 2. CONDUCTIVITIES (k) AND CONDUCTANCES (C) OF BUILDING 
MATERIALS AND INSULATORS Continued 

The efficients are expressed in Btu fer hour per square foot per degree Fahrenheit per 1 in. thickness, 
unless otherwise indicated. 



Material 


Description 


DENSITY 
(Ln PER Cu FT) 


MEAN TEMP. 
(DBG FAHR) 


CONDUCTIVITY (fc) 

OR 

CONDUCTANCE (C) 


~ js ^|O 

g Y E 

|si 1 

S S 5 


INSLT.ATION -LOOSE 
FILL OR BAT TYPE 
Continued 

GLASS Wool 
GRANULAR. 


Fibrous material made from dolomite and 
silica. .... i 


1.50 
9.40 

1.50 
4.20 

6.20 
30.00 
24.00 
18.00 
12.00 
34.00 
26.00 
24.00 
19.80 
18.00 

ITlO 
21.00 
18.00 
14.00 
10.00 
14.50 
14.50 
11.50 
12.00 
8.80 
13.20 
3.00 


75 
103 

75 
72 

42 
90 
90 
90 
90 
90 
90 
75 
90 
75 

90 
90 
90 
90 
90 
77 
75 
72 
90 
90 
90 
90 


0.27 
0.27 

0.27 
0.24 

0.32 
1.00 
0.77 
0.59 
0.44 
0.60 
0.52 
0.48* 
0.35 
0.34 
0.27* 
0.31 
0.30 
0.29 
0.28 
0.27* 
0.33 
0.38 
0.31 
0.41 
0.41 
0.36 
0.31 


3.70 (3) 
3.70 (1) 

3.70 (3) 
4.17 (3) 

3.12 3) 
.00 1) 
.30 1 
.69 1 
.27 1 
.67 1 
.92 1 
2.08 3) 
2.86 1) 
2.94 3) 
3.70 _ 
3.22 1) 
3.33 1 
3.45 1 
3.57 1) 
3.70 1) 
3.03 1) 
2.63 3) 
3.22 3) 
2.44 1 
2.44 1 
2.78 1) 
3.22 1) 


Fibrous material made from slag 
Fibrous material 25 to 30 microns in dia- 
meter, made from virgin bottle glass 
Made from combined silicate of lime and 
alumina 


MINERAL WOOL. 

RlORANULATZD COBK 

ROCK WOOL 


Made from expanded aluminum-magnesium 
silicate 


Cellular dry 




u 


ti a. 


Flaked dry and fluffy-' 
pjasea, ary ana nuny 




a u u u 


u u u u 


u u * u 


All forms typical t 


About 3to-in particles 


Fibrous material made from rock . 


SAWDUST^., ^ t _, T 


It U U U U 

ff u ft u a 

tt It U It 


Rock wool with a binding agent 
Rock wool with flax, straw pulp, and binder 
Rock wool with vegetable fibers 


Various , 


SHAVTWGS 


Various from planer 




From maple, beech and birch (coarse) 
Redwood bark 




INSULATION RIGID 
FEBBB 


Typical 


14760 
10.60 
7.00 
5.40 
14.50 

10.00 
15.00 
17.90 
15.20 

54.00 
16.10 
19.30 
24.20 
13.50 

13.80 
17.00 
15.90 
15.00 


90 
90 
90 
90 
90 

75 
71 
78 
70 

75 
81 
86 
72 
70 

70 
68 
72 
70 
52 
72 


0.30* 
0.34 
0.30 
0.27 
0.25 
0.32 
0.33* 

0.28 
0.33 
0.36 
0.32 

1.07f 
0.34 
0.51 
0.46 
0.33 

0.30 
0.33 
0.33 
0.33 
0.33 
0.29 
0.33 
0.34 


3.33 - 
2.94 (1) 
3.33 (1) 
3.70 (1) 
4.00 (1) 
3.12 (1) 
3.03 ._ 

3.57 3) 
3.03 3) 
3.12 4) 
3.12 3) 

0.93 3) 
2.94 3 
1.96 1 
2.17 3) 
3.03 3) 

3.33 3 
3.03 3 
3.03 3 
3.03 3) 
3.03 6) 
3.45 3) 
3.03 3) 
2.94 (1) 


No added binder 


tt a u 


UK u 


it it it 


Asphaltic binder .._. ._. 


Typical 




Chemically treated hog hair covered with 
film of asphalt 


Madfl from 1*1171 staHn? 


" exploded wood fibers 
tt hard wood fibers 
Insulating plaster 9/10-in. thick applied to 
|-in. plaster board base 


M?M?e from licorice roots 


Made from 85% magnesia and 15% asbestos 
Made from shredded wood and cement 
" a sjigar nans fiber, JL . 


Sugar cane fiber insulation blocks encased in 
asphalt membrane 


Made from wheat straw --,,-,-,, 


wnnd fiber 





B 


* 


8.50 
15.20 
16.90 





u 


90 


BUILDING BOARDS 
\SR-Kfrrnx 




123.00 
20.40 


86 
110 


2.70 

0.48 


0.37 (1) 
2.08 (2) 




Corrugated asbestos board 



For notes see Pa^e 97. 



100 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



TABLE 2. CONDUCTIVITIES (k) AND CONDUCTANCES (C) OF BUILDING 
MATERIALS AND INSULATORS Continued 

The coefficients are expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness 
unless otherwise indicated. 



Material 


Description 


DENSITY 
(La PER Cu FT) 


MBAN TBMP. 
(DEQ FAHR) 


CONDUCTIVITY (fc) 

OR 
CONDUCTANCE (C) 


~ \** ~ !cj 

i i 


! 


BUILDING BOARDS 
Continued 
ASBESTOS ~ 


Pressed asbestos mill board _ 

Sheet MhfiRtns 


60.50 
48.30 


86 
110 


0.84 
0.29 


1.19 
3 45 


(1) 

?) 


GYPSUM -... 


Gypsum between layers of heavy paper 
Rigid, gypsum between layers of heavy 
paper (H-in. thick) 


62.80 
53.50 


70 
90 


1.41 
2.60f 


0.71 
0.38 


3) 
(1) 


PLASTER BOARD.._ _ . 


Gypsum muted with sawdust between layers 
of heavy paper (0.39-in. thick) 
(*$ in ) 


60.70 


90 


3.60f 
3.73J* 


0.28 
0.27 


(1) 




(fcin.) - 








2.82f* 


0.35 


- 


ROOFING CONSTRUCTION 
ROOTING . - 


Asphalt, composition or prepared 


70 00 


75 


6 50t* 


15 


0) 




Built up- iNP 11 t n i ft k *" *" 






3.53f* 


0.28 






Built up, bitumen and felt, gravel or slag 
snrfaftftdff T T T 






1.33 


0.75 


(2) 




Plaster board, gypsum fiber concrete and 

3-ply roof roaring ?V i^ thick 


52 40 


76 


0.58f 


1.72 


4) 


SHTNGT/I&S -^ -. 


AaWWi 


65.00 


75 


6.00f* 


0.17 


3) 




At r hfl.|t 


70.00 


75 


6.50t* 


0.15 


3) 




RlfttA 


201.00 




10.37* 


10 


7) 




Wood 






1.28f* 


0.78 


















PLASTERING MATERIALS 
PLASTER 


foment 






8.00 


0.13 


(?) 




Gyp?UTn typififtl 






3.30* 


0.30 






Thifi1rr,P*s 3^ in 




73 


8.80t 


0.11 


(4) 


METAL T,ATW ^NP PT.ASTTB^ 


Total thielcnfisa % in. 






4.40t* 


0.23 




WOOD LATH AND PLASTER 


54-in. plaster, total thickness % in 





70 


2. 50t* 


0.40 


(4) 


BUILDING 
CONSTRUCTIONS 

FBAMD- 


1-in, fir sheathing and buiMing paper 




30 


0.71t* 


1.41 


(4) 




1-in. fir sheathing, building paper, and 




20 


O.SOf* 


2.00 


(4) 




1-in. fir sheathing, building paper and stucco 
Pine lap siding and building paper - ~siding 

4 in wi^e , !, 





20 
16 


0.55 
O.SSf* 


1.82 
1.18 


(4) 
(4) 




Yellow pine tap siding. .-- 






1.28t* 


0.78 




FLOORING ._ - 


Maple across grain..^_ .. , ^ 1J .., 


40.00 


75 


1.20 


0.83 


(3) 




Bfttt'fisnip linoleum (M-" 1 ) " 






1.36f* 


0.74 


















AIR SPACE AND SURFACE 
COEFFICIENTS 

Am ftPAdftH 


Over %-in. faced with ordinary building 














materials 




40 


I.IO"* 


0.91 


(4) 


SURFACES, ORDINARY 


fitill ur (/i) 






1.6St* 


0.61 


(4) 




15 mph (/o) . ,..... , ,- 






6. 00-* 


0.17 


(4) 


SURFACE ROUGH STUCCO 








p.oot* 


0.11 


(4) 


SURFACE, BRIGHT ALTTMTVTTM 


Still 9) f (/i) 11 






o.sot 


1.25 


() 
















AIR SPACES FACED WITH 
BRIGHT ALUMINUM 
FOIL 


Air space, faced one side with bright alumi- 
num foil over M-" 1 - win"fc 




50 


0.46f* 


2.17 


(4) 




Air space, faced one side with bright alumi- 
num foil iHj-in wide 




50 


62t 


1.61 


(4) 




Air space,' faced both sides. with bright 
aluminum foil, over %-in. wido , ., 
Air space, faced both sides with bright 
aluminum foiL ^-in wiH^, rT , T 





50 
50 


0.41f* 
O.S7f 


2.44 
1.75 


(4) 
(4) 



For notes see Page 97. 



101 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 2. CONDUCTIVITIES (A) AND CONDUCTANCES (C) OF BUILDING 
MATERIALS AND INSULATORS Continued 

The coefficients are expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness, 
unless otherwise indicated. 



Material 


Description 


DBNBPrr 
(La PER Cu FT) 


LMEAN TEMP. 
(Duo FAHR) 


CONDUCTIVITY (Jk) 

OR 

CONDUCTANCE (C) 


H* -<|o 


AIR SPACES FACED WITH 
BRIGHT ALUMINUM 
FOILContinued 


Air space divided in two with single curtain 
of bright aluminum foil (both sides bright) 
Each space over ?^i"in wide 




50 


0.23f* 


4.35 (4) 




Each gp&ce J^o-in. wide . . ,.,.., 




SO 


0.31f 


3.23 (4) 




Air space with multiple curtains of bright 
aluminum foil bright on both sides, 
curtains more than %-in. apart, ah* circu- 
lation between spaces prevented: 
2 curtains fonnjpg 3 npfurflfi 




50 


O.lSf* 


6.78 (4) 




3 curtains forming 4 spaces 




50 


O.llf* 


9.22 (4 




4 curtains forming 5 spaces L -. L ^,, r 




50 


0.09f* 


11.66 (4 














SPACES FACED WITH NOX- 
METALLIC REFLECTIVE 
SURFACE 


Fabric with non-metallic reflective surface 
06 in. thick) placed in center of a 1M in- 

ftir spare 




70 


0.33f 


3.03 (4) 




Core o'f fiber board coated two sides with 
non-metallic reflective surface (% in. 
thick) placed in space having approxi- 
mately % in. air space on each side 
Fiber board coated one side with non- 
metallic reflective surface (% in. thick) 
placed in space having approximately 
* in air space on each side 


23.4 


70 
75 


0.27f 
0.49f 


3.70 (3) 
2.04 (3) 




Air space divided in two with fabric faced 
both sides with non-metallic reflective 
surface, each space over %-in. wide 
Air space over J^-in. wide faced one side 
with non-metallic reflective surface 





40 
40 


0.33f 
0.67f 


3.03 (4) 
1.49 (4) 


WOODS (Across Grain) 
RA.TJU 




20.0 


90 


0.58 


1.72 (1) 






8.8 


90 


0.38 


2.63 ) 






7.3 


90 


0.33 


3.03 ) 


CALIFORNIA. REDWOOD 


QO7 TnoTfitdire 


22.0 


75 


0.66 


1.53 ) 




QCT 


28.0 


75 


0.70 


1.43 ) 




R? 


22.0 


75 


0.70 


1.43 ) 




8 07 


28.0 


75 


0.75 


1.33 ) 




16 or 


22.0 


75 


0.74 


1.35 ) 




Ifi^jj 


28.0 


75 


0.80 


1.25 4) 


CYPRXSB 




28.7 


86 


0.67 


1.49 1) 


DoijoffAs FIR 


0% moisture . , ... 


26.0 


75 


0.61 


1.64 4) 






34.0 


75 


CT.67 


1.49 4) 




R<7 


26.0 


75 


0.66 


1.52 4) 




fl^ 


34.0 


75 


0.75 


1.33 4) 




16% . , 1Lll t 


26.0 


75 


0.76 


1.32 4) 






34.0 


75 


0.82 


1.22 4) 


EAHTWN HmnxCif 


Cty Tnniftf.nre 


22.0 


75 


0.60 


1 67 4) 




ftor 


30.0 


75 


0.76 


1.32 4) 




R% 


22.0 


75 


0.63 


1.59 4) 




9P7 


30.0 


75 


0.81 


1.23 4) 




16% 


22.0 


75 


0.67 


1.49 (4) 






30.0 


75 


0.85 


1.18 (4) 


HARD MAPLJC.. ... 


0*7 mofctrire 


40.0 


75 


1.01 


0.99 (4) 




QOT 


46.0 


75 


1.05 


95 4) 




W/ 


40.0 


75 


1.08 


0.93 4) 




s% 


46.0 


75 


1.13 


0.89 4) 




16% 


40.0 


75 


1.15 


0.87 4) 




Ifi % 


46.0 


75 


1.21 


0.83 4) 















For notes see Page 97. 



102 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND T ABIDES 



TABLE 2. 



CONDUCTIVITIES (k) AND CONDUCTANCES (O OF BUILDING 
MATERIALS AND INSULATORS Continued 



The coefficients are expressed in Btu per hour per square foot per degree Fahrenheit per 1 in. thickness, 
unless otherwise indicated. 



Material 


Description 


DKNSITT 
(La pin Cu FT) 


MEAN TEMP. 
(DEQ FAHR) 


CONDUCTIVITT (k) 
on 
CONDUCTANCB (C) 


-'* ^'0 

s & 


j 


WOODS Continued 
LONGLIBAF YELLOW Pirns 


0% moisture __, Tir , r 


30.0 


7S ! 


0.76 


1.32 


f4) 






40.0 


75 


0.86 


1.16 


(4) 




R<y 


30.0 


75 


0.83 


1.21 


(4) 




gar 


40.0 


75 ! 


0.95 


1.05 


(4) 




Ifi% ril ... , __.,., 


30.0 


7S 


0.89 


1.12 


(4) 




16% 


40.0 


75 


1.03 


0.97 


(4) 


MAHQGANT 




34.3 


86 


0.90 


1.11 


(1) 


MjLPT.TH 




44.3 


86 


1.10 


0.91 


(1) 


\IAPLIB OB OAK_ 








1.15* 


0.87 




NORWAY PINE 


0% moisture - 


22.0 


75 


0.62 


1.61 


(4) 






32.0 


75 


0.74 


1.35 


4) 




oCff 


22.0 


75 


0.68 


1.47 


4) 




ty? 


32.0 


75 


0.83 


1.21 


4) 




16% ,, L 


22.0 


75 


0.74 


1.35 


4) 




16% 


32.0 


75 


0.91 


1.10 


4) 


TJ CfWXBS 


0% moisture ... L 


22.0 


75 


0.67 


1.49 


4) 






32.0 


75 


0.79 


1.27 


4) 




ow 


22.0 


75 


0.71 


1.41 


4) 




gar 


32.0 


75 


0.84 


1.19 


4) 




169 r 


22.0 


75 


0.74 


1.35 


4) 




16% 


32.0 


75 


0.90 


1.11 


4) 


RED OAK 


0% m^i"? ure 


38.0 


75 


0.98 


1.02 


4) 






48.0 


75 


1.18 


0.85 


4) 




oar 


38.0 


75 


1.03 


0.97 


4) 




oft? 


48.0 


75 


1.24 


0,81 


4) 




16% 


38.0 


75 


1.07 


0.94 


4) 




16% 


48,0 


75 


1.29 


0.78 


4) 


SHQBTLHAi 1 YBLLOW PINTS 




26.0 


75 


0.74 


1.35 


4) 






36.0 


75 


0.91 


1.10 


4) 




oar 


26.0 


75 


0.79 


1.27 


4) 




Offi? 


36.0 


75 


0.97 


1.03 


4) 




16?^ 


26.0 


75 


0.84 


1.19 


4^ 




16% 


36.0 


75 


1.04 


0.96 


4) 


BofT KLM 




28.0 


75 


0.73 


1.37 


4) 




QOT 


34.0 


75 


0.88 


1.14 


L) 




gar 


28.0 


75 


0.77 


1.30 


4) 




8y 


34.0 


75 


0.93 


1.08 


4) 




169^ 


28.0 


75 


0,81 


1.24 


4 




jgar 


34.0 


75 


0.97 


1.03 


t 


SOFT MAPLE- 


0^ moisture 


36.0 


75 


0.89 


1.12 


4) 




09* 


42.0 


75 


0.95 


1.05 


4) 




8?^ 


36.0 


75 


0.96 


1.04 


4) 




007 


42.0 


75 


1.02 


0.98 


4) 




16^ 


36.0 


75 


1.01 


0.99 


4) 




16*7 


42.0 


75 


1.09 


0.92 


4 


SUGAR PTNIE 


0% moiB ure ...L.,^ , . r 


22.0 


75 


0.54 


1.85 


4 






28.0 


75 


0.64 


1.56 


4 




8v 


22.0 


75 


0.59 


1.70 


4} 




oof 


28.0 


75 


0.71 


1.41 


4} 




169^ 


22.0 


75 


0.65 


1.54 


4) 




167 


28.0 


75 


0.78 


1.28 


4) 


VIRGINIA. PINB 





34.3 


86 


0.96 


1.04 


1) 


WEST COAST BJBMLOCK. 


0% moisture -..r. 


22.0 


75 


0.68 


1.47 


4) 






30.0 


75 


0.79 


1.27 


4) 




Ott? 


22.0 


75 


0.73 


1.37 


4} 




am 


30.0 


75 


0.85 


1.18 


4) 




16v 


22.0 


75 


0.78 


1.28 


4) 




jg07 


30.0 


75 


0.91 


1.10 


4) 


WH p___ 




31.2 


86 


0.78 


1.28 


1) 


YELLOW PTKB 








1.00 


1.00 


3) 










0.80* 


1.25 




















For notes see Page 97. 



103 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 3. COEFFICIENTS OF TRANSMISSION (U) OF MASONRY WALLS* 

Coefficients are expressed in Blu per hour per square foot per degree 
Fahrenheit difference in temperature between the air on the two sides, 
and are based on a wind Telocity of 15 mph. 













} 


















THICKNESS 






T 


YP 


ICAL 




OF 


WALL 


CONSTRUCTION TYPE OF WALL 


MASONRY 


No. 














(INCHES) 






r< 
=3*5 

aa= 


a 

3t 


P* 

i 


=S ^ 

3 

*>H 


^> 

& 




Solid Brick 

Based on 4-in. hard brick and the remainder 


8 
12 


1 
2 




^a 
te*= 

*** 


=2** 




s 

**. 


^2 
3? 


t 




common brick. 


16 


3 




t 


3^ 


g 


./TU&C( 
ss*^S 


)N 


Hollow Tile 

Stucco Exterior Finish. 
The 8-in. and 10-in. tile figures are based on 


8 


4 


1 


^5 


!S 7 
















B 






two cells in the direction of flow of heat. The 


10 














Q 






12-in. tile is based on three cells in the direc- 


12 


6 






y 






g 






tion of flow of heat. The 16-in. tile consists 


16 


7 




1 


I 






1 


r 


^ 


of one 10-in. tile and one 6-in. tile each having 






*4K 


UL 


, 


**^ 


r 

r 




two cells in the direction of heat flow. 






c 


t 


C! 

"^ 


5 


9 




8 


8 


N. 




Jar: 


%<? 


e^i 




12 


9 


L 


^ 


P 


T^ 


^J 


Limestone or Sandstone 


16 


10 


c 




Sfe 

"^. 


a? 

^jx 


? 




24 


11 












Concrete (Monolithic) 

These figures may be used with sufficient 


6 
10 


12 
13 












accuracy for concrete walls with stucco 


16 


14 




"^ -N, 




v."j 


( 


exterior finish. 


20 


15 








9 


0. 


^ ' 


: 




6 


16 


















Cinder (Monolithic) 

Conductivity k ~> 4.36 


10 
16 


17 
18 




y 




9 




:' 


~A 




20 


19 


-. 




!. 


" 


*f 






6 


20 








I^J^- 




Haydite (Monolithic) 


10 


21 












Conductivity k = 3.96 


16 


22 














20 


23 












Cinder Blocks 


8 


24 












Cores filled with dry cinders, 69.7 Ib per cu ft. 
Cores filled with granulated cork, 5.12 Ib 


8 


25 












per cu ft. 


8 


26 












Cores filled with rock wool, 14.2 Ib per cu ft. 
Based on one air cell in direction of heat flow. 
Cores filled with granulated cork, 5.24 Ib per 


8 
12 


27 
28 










4^> 


*-^ 


\ 




cu ft. 
Concrete Blocks 


12 


29 


8 


30 




a- 








^ 


\ 




Cores filled with granulated cork, 5.14 Ib per 










=35333 


SSE 


"53S. 


* 


y 




cuft. 


8 


31 


**** 


"-^ 


C 




/ 


Or 


Based on one air cell in direction of heat flow. 


12 


32 








l^ 




Haydite Blocks 


8 


33 












Cores filled with granulated cork, 5.06 Ib per 
















cuft. 


8 


34 












Haydite Blocks 


12 


35 












Cores filled with granulated cork r 5.6 Ib per 
















cu ft. 


12 


36 



Computed from factors marked by * in Table 2. 
*Based on the actual thickness of 2-in. furring strips. 

104 



CHAPTER 5, HEAT TRANSMISSION COEFFICIENTS AND TABLES 



INTERIOR FINISH 



UNINSULATED WALLS 


INSULATED WALLS 


Plain walls no in- 
terior finish 


g 

S" 
3 

II 


1 

1 

5J2 


'"'"'.3 


* 
O 

!l! 

S-P.S 


Decorated building 
board (M in.) with- 
out plaster furred 


"$ 
^ 

-S o 


. 

Si"! 


g ?3 

3s| 

lib 

I1s5 


si in* 

-dlf^S 
*l*89*3 

j^y 

Pi S-2J2\o"3 


Plaster on metal 
lath attached to fur- 
ring strips (2 in.*) 
rock wool fill (155 
in.&) 


gjp.si.1 
52 till 1 
llsSiJI 


A 


B 


C 


D 


E 


F 


G 


H 


I 


J 


K 


L 


0.50 
0.36 
0.28- 


0.46 
0.34 
0.27 


0.30 
0.24 
0.20 


0.32 
0.25 
0.21 


0.30 
0.24 
0.20 


0.23 
0.19 
0.17 


0.22 
0.19- 
0-16- 


0.16 
0.14 
0.13 


0.14 
0.12 
0.11 


0.23 
0.19 
0.17 


0.12 
0.11 
0.10 


0.20 
0.17 
0.15 


0.40 
0.39 
0.30 
0.25 


0.38 
0.37 
0.29 
0.24 


0.26 
0.26 
0.22 
0.19 


0.28 
9.27 
0.22 
0.19 


0.26 
0.26 
0.22 
0.19 


0.20 
0.20 
0.17 
0.16 


0.20 
0.19 
0.17 
0.15 


0.15 
0.15 
0.14 
0.12 


0.13 
0.13 
0.12 
0.11 


0.20 
0.20 
0.18 
0.16 


0.11 
0.11 
0.10 
0.097 


0.18 
0.18 
0.16 
0.14 


0.71 
0.58 
0.49 
0.37 


0.64 
0.53 
0.45 
0.35 


0.37 
0.33 
0.30 
0.25 


0.39 
0.34 
0.31 
0.26 


0.37 
0.33 
0.30 
0.25 


0.26 
0.24 
0.22 
0.20 


0.25 
0.23 
0.22 
0.19 


0.18 
0.17 
0.16 
0.15 


0.15 
0.14 
0.14 
0.13 


0.26 
0.24 
0.22 
0.20 


0.13 
0.13 
0.12 
0.11 


0.23 
0.21 
0.20 
0.18 


0.79 
0.62 
0.48 
0.41 


0.70 
0.57 
0.44 
0.39 


0.39 
0.34 
0.29 
0.27 


0.42 
0.37 
0.31 
0.28 


0.39 
0.34 
0.29 
0.27 


0.27 
0.25 
0.22 
0.21 


0.26 
0.24 
0.21 
0.20 


0.19 
0.18 
0.16 
0.15 


0.16 
0.15 
0.14 
0.13 


0.27 
0.25 
0.22 
0.21 


0.13 
0.13 
0.12 
0.12 


0.23 
0.22 
0.20 
0.18 


0.46 
0.33 
0.22 
0.19 


0.43 
0.31 
0.22 
0.18 


0.29 
0.23 
0.17 
0.15 


0.30 
0.24 
0.18 
0.15 


0.29 
0.23 
0.17 
0.15 


0.22 
0.18 
0.15 
0.13 


0.21 
0.18 
0.14 
0.13 


0.16 
0.14 
0.12 
0.11 


0.14 
0.12 
0.10 
0.09 


0.22 
0.18 
0.15 
0.13 


0.12 
0.11 
0.09 
0.09 


0.19 
0.16 
0.13 
0.12 


0.44 
0.30 
0.21 
0.17 


0.41 
0.29 
0.20 
0.17 


0.28 
0.22 
0.16 
0.14 


0.29 
0.23 
0.17 
0.14 


0.28 
0.22 
0.16 
0.14 


0.21 
0.17 
0.14 
0.12 


0,21 
0.17 
0.14 
0.12 


0.16 
0.14 
0.11 
0.10 


0.13 
0.12 
0.10 
0.09 


0.21 
0.18 
0.14 
0.12 


0.12 
0.10 
0.09 
0.08 


0.19 
0.16 
0.13 
0.11 


0.42 
0.31 


0.39 
0.29 


0.27 
0.23 


0.28 
0.23 


0.27 
0.22 


0.21 

0.18 


0.20 
0.17 


0.16 
0.14 


0.13 
0.12 


0.21 
0.18 


0.12 
0.11 


0.19 
0.16 


0.22 
0.23 
0.37 


0.21 
0.22 
0.35 


0.17 
0.19 
0.25 


0.18 
0.18 
0.26 


0.17 
0.18 
0.25 


0.14 
0.15 
0.19 


0.14 
0.14 
0.19 


0.12 
0.12 
0.15 


0.11 
0.10 
0.13 


0.14 
0.15 
0.19 


0.09 
0.09 
0.11 


0.13 
0.14 
0.17 


0.20 


0.19 


0.17 


0.16 


0.16 


0.13 


0.13 


0.11 


0.10 


0.14 


0.09 


0.13 


0.56 


0.52 


0.32 


0.34 


0.32 


0.24 


0.23 


0.17 


0.14 


0.24 


0.12 


0.21 


0.41 
0.49 


0.39 
0.46 


0.27 
0.30 


0.28 
0.32 


0.27 
0.30 


0.21 
0.23 


0.20 
0.22 


0.15 
0.16 


0.13 
0.14 


0.21 
0.23 


0.12 
0.12 


0.18 
0.20 


0.36 


0.34 


0.26 


0.26 


0.24 


0.19 


0.19 


0.15 


0.13 


0.19 


0.11 


0.17 


0.18 


0.17 


0.15 


0.15 


0.14 


0.13 


0.12 


0.10 


0.09 


0.13 


0.08 


0.12 


0.34 


0.32 


0.25 


0.25 


0.24 


0.19 


0.18 


0.14 


0.12 


0.19 


0.11 


0.17 


0.15 


0.14 


0.13 


0.13 


0.12 


0.11 


0.11 


0.09 


0.08 


0.11 


0.08 


0.10 



e A waterproof membrane should be provided between the outer material and the insulation fill to 
prevent possible wetting by absorption and a subsequent lowering of efficiency. 

105 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 4. COEFFICIENTS OF TRANSMISSION (Z7) OF MASONRY WALLS 
WITH VARIOUS TYPES OF VENEERS* 



Coefficients are expressed in Blu per hour per square foot per degree 
Fahrenheit difference in temperature between the air on the two sides, 
and are based on a wind velocity of Iff mph. 



TYPE OF WALL 



TYPICAL 
CONSTRUCTION 



BACKING 



WALL 

No. 




6 in. 





4 in. Brick Veneer* 



Hollow THe* 



12 in. 



4 in. Brick Veneer* 



6 in. 
10 in. Concrete 

16 in. 



8 in. Cinder Blocks 

8 in. Cinder Blocks Cores 

filled with granulated cork, 

5.12 Ib per cu ft. 
12 in. Cinder Blocks 
12 in. Cinder Blocks Cores 
filled with granulated cork, 
5.24 Ib per cu ft. 



4 in. Brick Veneer* 



8 in. Concrete Blocks 

8 in. Concrete Blocks Cores 

filled with granulated cork, 

5.14 Ib per cu ft. 
12 in. Concrete Blocks 

8 in. Haydite Block 

8 in. Haydite Block Cores 

filled with granulated cork, 

5.06 Ib per cu ft. 
12 in. Haydite Block 
12 in. Haydite Block Cores 

filled with granulated cork, 

5.6 per cu ft. 



4 in. Cut-Stone Veneer* 



Sin. 

12 in. Common Brick 
16 in. 



6 in. 



4 in. Cut-Stone Veneer 1 



Hollow me* 



12 in. 



4 in. Cut-Stone Veneer 1 



6 in. 
10 in. Concrete 

16 in. 



37 
38 
39 
40 



41 
42 
43 



44 



45 
46 



47 



48 



49 
50 
51 



52 
53 



54 



55 
56 

57 



58 
59 
60 
61 



62 
63 
64 



puted from factors marked by * in Table 2. 

d on the actual thickness of 2-in. furring strips. 

<The 6-in., 8-in. and 10-in. tile figures are based on two cells in the direction of heat flow. The 12-in. 
tHe is based on three cells in the direction of heat flow. 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



INTERIOR FINISH 



UNINSULATED WALLS 


INSULATE) WALLS 


i 

.5 S 




3 

3 

If 


g| 

S3i 


g-g 

3 
ii 

PU 8 


gg 

li-p 

ill 


No plaster deco- 
rated rigid or build- 
ing board interior 
finish (ft in.)- 
furred 


S 

1 


1 

* 1 

|:3 


Plaster (J$ in.) on 
cork board (1H in.) 
setincementmortar 
(H in.) 


11 sill 

Sj-slfll 


lt| 

3i*Jk 

aSif-* 

j|jJ5g 

slssa 


Plaster (H in.) on 
metal lath attached 
to furring stripe 
(2 in.*) flexible in- 
eulation (H in.) be- 
tween furring strips 
(one air space) 


A 


B 


C 


D 





F 


G 


H 


I 


J 


K 


L 


0.36 
0.34 
0.34 
0.27 


0.34 
0.33 
0.32 
0.26 


0.24 
0.24 
0.23 
0.20 


0.25 
0.25 
0.24 
0.21 


0.24 
0.24 
0.23 
0.20 


0.19 
0.19 
0.19 
0.16 


0.19 
0.18 
0.18 
0.16 


0.16 
0.14 
0.14 
0.13 


0.13 
0.12 
0.12 
0.11 


0.19 
0.19 
0.19 
0.16 


0.11 
0.11 
0.11 
0.10 


0.17 
0.17 
0.17 
0.15 


0.57 
0.48 
0.39 


0.53 
0.45 
0.37 


0.33 
0.30 
0.26 


0.35 
0.31 
0.27 


0.33 
0.30 
0.26 


0.24 
0.22 
0.20 


0.23 
0.22 
0.19 


0.17 
0.16 
0.15 


0.14 
0.14 
0.13 


0.24 
0.22 
0.20 


0.13 
0.12 
11 


0.21 
0.20 
0.18 


0.35 


0.33 


0.24 


0.25 


0.24 


0.19 


0.18 


0.14 


0.12 


0.19 


0.11 


0.17 


0.20 
0.31 


0.19 
0.30 


0.16 
0.22 


0.16 
0.23 


0.16 
0.22 


0.13 
0.18 


0.13 
0.17 


0.11 
0.14 


0.10 
0.12 


0.13 
0.18 


0.09 
0.11 


0.12 
0.16 


0.18 


0.18 


0.15 


0.15 


0.15 


0.13 


0.12 


0.10 


0.09 


0.13 


0.08 


0.12 


0.44 


0.42 


0.28 


0.30 


0.28 


0.21 


0.21 


0.16 


0.13 


0.21 


0.12 


0.19 


0.34 
0.40 
0.31 


0.32 
0.38 
0.29 


0.24 
0.26 
0.23 


0.25 
0.28 
0.23 


0.23 
0.26 
0.22 


0.19 
0.20 
0.18 


0.18 
0.20 
0.17 


0.14 
0.15 
0.14 


0.12 
0.13 
0.12 


0.19 
0.20 
0.18 


0.11 
0.11 
0.11 


0.17 
0.18 
0.16 


0.17 
0.29 


0.16 
0.28 


0.14 
0.21 


0,14 
0.22 


0.14 
0.21 


0.12 
0.17 


0.12 
0.17 


0.10 
0.13 


0.09 
0.12 


0.12 
0.17 


0.08 
0.10 


0.11 
0.16 


0.14 


0.14 


0.12 


0.12 


0.12 


0.10 


0.10 


0.09 


0.08 


0.10 


0.07 


0.10 


0.37 
0.28 
0.23 


0.35 
0.27 
0.22 


0.25 
0.21 
0.18 


0.26 
0.21 
0.18 


0.25 
0.21 
0.18 


0.19 
0.17 
0.15 


0.19 
0.16 
0.14 


0.15 
0.13 
0.12 


0.13 
0.12 
0.11 


0.19 
0.17 
0.15 


0.11 
0.10 
0.095 


0.17 
0.15 
0.14 


0.37 
0.36 
0.35 
0.28 


0.35 
0.34 
0.33 
0.26 


0.25 
0.24 
0.24 
0.20 


0.26 
0.25 
0.25 
0.21 


0.25 
0.24 
0.24 
0.20 


0.20 
0.19 
0.19 
0.17 


0.19 
0.19 
0.18 
0.16 


0.15 
0.15 
0.14 
0.13 


0.13 
0.13 
0.12 
0.11 


0.20 
0.19 
0.19 
0.17 


0.11 
0.11 
0.11 
0.10 


0.18 
0.17 
0.17 
0.15 


0.61 
0.51 
0.41 


0.56 
0.47 
0.38 


0.34 
0.31 
0.26 


0.36 
0.32 
0.28 


0.34 
0.31 
0.26 


0.25 
0.23 
0.20 


0.24 
0.22 
0.20 


0.18 
0.17 
0.15 


0.15 
0.14 
0.13 


0.25 
0.23 
0.21 


0.13 
0.12 
0.11 


0.22 
0.20 
0.18 



'Calculations include cement mortar (H in.) between veneer or facing and backing. 
'Based on one air cell in direction of heat now. 

/A waterproof membrane should be provided between the outer material and the insulation fill to 
prevent possible wetting by absorption and a subsequent lowering of efficiency. 

107 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 5. COEFFICIENTS OF TRANSMISSION (27) OF 
VARIOUS TYPES OF FRAME CONSTRUCTION* 



These coefficients ere expressed in Btu per hour per square foot per 
degree Fahrenheit difference in temperature between the air on the two 
sides, and are based on a wind velocity of 15 mph. 



TYPICAL 
CONSTRUCTION 


i 

'. EXTERIOR FINISH 

i 


TYPE OF SHEATHING 


WALL 
No. 


rssT^fi 

^ 

LJO^?; 

^/Hfcvr 

/WIVV J; 

U* 

/HtAT 

"i ijr "^** 

/HEAT 
/WA 

/Kt 


i 

1 

K" JM 

MHG. 

*80 

ttiHCi 

HWG 
TtK< 

P 

KING 
>UC1 

1 

rx 

KIKS 


, 

1 

1 
J/. 

r 

\ 

1 

\ 

c.\ 

> 


Wood Siding or Clapboard 


1 in. Wood* 


65 


2 %2 in- Rigid Insulation 


66 


^ in. Plaster Board 


67 


Wood Shingles 


1 in. Wood* 


68 


% in. Rigid Insulation* 


69 


% in. Plaster Board* 


70 


Stucco 


1 in. Wood* 


71 


2 % 2 in. Rigid Insulation 


72 


M in. Plaster Board 


73 


Brick/ Veneer 


1 in. Wood* 


74 


% in. Rigid Insulation 


75 


}i in. Plaster Board 


76 



"Computed from factors marked by * in Table 2. 
plaste? board^ "** 8 ^^ ^ be ^^ ^^ sufficient accurac y for plaster on wood lath or plaster on 
Based on the actual width of 2 by 4-in. studding, namely, 35i in. 



108 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



INTERIOR FINISH 



No INSULATION* BETWEEN STUDDING 



INSULATION BETWEEN STUDDING 



I 

5 
5 
J3 

3 

i 


5 

J3 
J 

g 

S 


if 

II 


1 

a 


ll 

& 
Is 


Plaster (^ in.) on rigid insulation 
(H in.) on studding 


i 

~i 
s! 



|3 


Plaster tt in.) on corkboard UH in.) 
on studding 


No piaster decorated rigid or build- 
ing board interior finish (J-a in.) 


1 in. wood sheathing, 1 * furring strips, 
plaster (H in.) on wood lath 


!.- 

ji 

o o 

3 -!s 

SJi 

tt _g 


Plaster (4 m.) on metal lath* on 
studding flexible insulation (? in.) 
between studding and in contact with 
sheathing 


3 

5| | 

* 

B.ST 

c^i 

.111 

gr* 

*-.s| 
ill 

PH^aJS 


Plaster (H in.) on metal lath h on 
studding flexible insulation (1 in.) 
between studding 2 air spaces 


Plaster (4 in.) on metal lath fc on 
studding rock wool fill (3 fi in. c ) 
between studding"* 


A 


B 


c 


D 


E 


F 


G 


H 


I 


J 


K 


L 


M 


0.25 


0.26 


0.25 


0.19 


0.15 


0.11 


0.19 


0.17 


0.20 


0.17 


0.15 


0.12 


0.072 


0.23 


0.24 


0.23 


0.18 


0.14 


0.11 


0.18 


0.14 


0.19 


0.17 


0.13 


0.10 


0.070 


0.31 


0.33 


0.31 


0.22 


0.17 


0.13 


0.23 


0.19 


0.24 


0.20 


0.17 


0.13 


0.076 


0.25 


0.26 


0.25 


0.19 


0.15 


0.11 


0.19 


0.17 


0.20 


0.17 


0.15 


0.12 


0.072 


0.19 


0.20 


0.19 


0.15 


0.12 


0.10 


0.16 


0.14 


0.16 


0.14 


0.11 


0.094 


0.066 


0.24 


0.25 


0.24 


0.19 


0.15 


0.11 


0.19 


0.19 


0,19 


0.17 


0.15 


0.12 


0.071 


0.30 


0.31 


0.30 


0.22 


0.16 


0.12 


0.22 


0.19 


0.23 


0.20 


0.17 


0.13 


0.076 


0.27 


0.29 


0.27 


0.20 


0.16 


0.12 


0.21 


0.15 


0.22 


0.19 


0.14 


0.11 


0.074 


0.40 


0.43 


0.40 


0.26 


0.19 


0.14 


0.28 


0.22 


0.29 


0.24 


0.20 


0.14 


0.081 


0.27 


0.28 


0.27 


0.20 


0.15 


0.12 


0.21 


0.17 


0.21 


0.18 


0.16 


0.12 


0.074 


0.25 


0.26 


0.25 


0.19 


0.15 


0.11 


0.19 


OJL5 


0.20 


0.18 


0.13 


0.11 


0.072 


0.35 


0.37 


0.35 


0.24 


0.18 


0.13 


0.25 


0.21 


0.26 


0.22 


0.18 


0.14 


0.079 



*Yellow pine or fir actual thickness about % in. 
Furring strips between wood shingles and sheathing. 

/Small air space and mortar between building paper and brick veneer neglected. 

A waterproof membrane should be provided between the outer material and the insulation fill to 
prevent possible wetting by absorption and a subsequent lowering of efficiency. 
A Stud and rock wool fill areas combined. 



109 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 6. COEFFICIENTS OF TRANSMISSION (U) OF FRAME INTERIOR WALLS 
AND PARTITIONS** 

Coefficients are expressed in Btu per hour per square foot per degree Fahrenheit difference in temperature 
between the air on the two sides, and are based on still air (no wind) conditions on both sides. 



TYPICAL CONSTRUCTION 


WALL 
No. 


SINGLE 
PARTITION 
(FINISH 
ON ONE 
SIDE OF 
STUDDING) 


DOUBLE PARTITION 
(FINISHED ON BOTH SIDES OP STUDDING) 


Air 
Space 
Between 
Studding 


Flaked 

G ffi* 
Between 
Studding 


Rock 
Wool 
Fill* 
Between 
Studding 


'Menble 
Insulation 
Between 
Studding 
(One Air 
Space) 


Stud Space Faced 
One Side with 
Bright Aluminum 
Foil 


TYPE OF WALL 




A 


B 


C 


D 


E 


F 


Wood Lath and Plaster 
On Studding 


77 


0.62 


0.34 


0.11 


0.076 


0.21 


0.24 


Metal Lath and Plaster* 

On Studding 


78 


0.69 


0.39 


0,11 


0.078 


0.23 


0.26 


Plaster Board (% in.) and 
Plaster* On Studding 


79 


0.61 


0.34 


0.10 


0.075 


0.21 


0.24 


M in. Rigid Insulation and 
Plaster* On Studding 


80 


0.35 


0.18 


0.083 


0.063 


0.14 


0.15 


1 in. Rigid Insulation and 
Plaster* On Studding 


81 


0.23 


0.12 


0.066 


0.054 


0.097 


0.10 


1H in. Corkboard and 
Plaster* On Studding 


82 


0.16 


0.081 


0..052 


0.044 


0.070 


0.073 


2 in. Corkboard and 
Plaster* On Studding 


83 


0.12 


0.063 


0.045 


0.038 


0.057 


0.059 



Computed from factors marked by * in Table 2. 'Plaster on metal lath assumed %-in. thick. 
*Thickness assumed 3^ inu 'Plaster assumed H-in- thick. 



TABLE 7. COEFFICIENTS OF TRANSMISSION (27) OF MASONRY PARTITIONS^ 

Coefficients are expressed in Btu per hour per square foot per degree Fahrenheit difference in temperature 
between the air on the two sides, and are based on still air (no wind) conditions on both sides. 



TYPICAL CONSTRUCTION 












W *S^^^ 


r 






WALLS 


WALLS 


I 






No. 


PLAIN WALLS 
(No PLASTER) 


PLASTERED 
ON ONE SIDE 


PLASTERED 
ON BOTH SIDES 


TYPE OF WALL 




A 


B 


C 


4-in. Hollow Clay Tile 
4-in. Common Brick 




84 
85 


0.45 
0.50 


0.42 
0.46 


0.40 
0.43 


4-in. Hollow Gypsum Tile 




86 


0.30 


0.28 


0.27 


2-in. Solid Plaster 




87 








0.53 



Computed from factors marked by * in Table 2. 

110 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



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and 



8. COEFF 
e expressed in 








I 










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s 



2ij5 







H 



s 



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factors marked 
ed to be % in. 
ed to be % in. 



21! 
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.3 cs o 

1 



111 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



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112 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



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113 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 11. COEFFICIENTS OF TRANSMISSION (U) OF VARIOUS TYPES 
OF FLAT ROOFS COVERED WITH BUILT-UP ROOFING* 



TYPICAL CONSTRUCTION 



WITHOUT CEILINGS 



WITH METAL LATH 

AND 
PLASTER CEILINGS* 



TYPE OF ROOF DECK 



THICKNESS 

OF 

ROOF 
DECK 

(INCHES) 



No. 




Precast Cement Tile 





Concrete 
Concrete 
Concrete 




m 



Wood 
Wood 
Wood 
Wood 



1* 

& 

4 




Gypsum Fiber Concrete 
(2 in.) on Plaster Board 
(Mm.) 

Gypsum Fiber Concrete* 
(3 in.) on Plaster Board 



Gypsum Fiber Concrete* 
(2 in.) on Rigid Insula- 
lation Board (H in.) 

Gypsum Fiber Concrete* 
(2 in.) on Rigid Insula- 
tion Board (1 in.) 



10 



12 





Flat Metal Roofs 

Coefficient of transmis- 
sion of bare corrugated 
iron (no roofing) is 1.50 
Btu per hour per square 
foot of projected area per 
degree Fahrenheit dif- 
ference in temperature, 
based on an outside wind 
velocity of 15 mph. 



13 



Computed from factors marked by * in Table 2. 

^Nominal thicknesses specified actual thicknesses used in calculations. 

Gypsum fiber concrete- -87}$ per cent gypsum, 12H per cent wood fiber. 



114 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



Coefficients are expressed in Btu per hour per square foot per degree 
Fahrenheit difference in temperature between the air on the two sides, 
and are based on an outside wind velocity of 15 mph. 



WITHOUT CEILING UNDER SIDE OF 
ROOF EXPOSED 


WITH METAL LATH AND 
PLASTER CEILINGS* 


No Insulation 


I 


3 


2 


3 




2 


.2 

c*> 


1 
I 


3 

5 


.? 


EJ 


es 




3 

1 


CM 


| 


1 

i 

a 


} 


| 

S 


.5 
^ 


j 


1 


1 
1 


1 





A 


B 


c 


D 


E 


F 


G 


H 


I 


j 


K 


L 


M 


N 





P 


0.84 


0.37 


0.24 


0.18 


0.14 


0.22 


0.16 


0.13 


0.43 


0.26 


0.19 


0.15 


0.12 


0.18 


0.14 


0.11 


0.82 
0.72 
0.64 


0.37 
0.34 
0.33 


0.24 
0.23 
0.22 


0.17 
0.17 
0.16 


0.14 
0.13 
0.13 


0.22 
0.21 
0.21 


0.16 
0.16 
0.15 


0.13 
0.12 
0.12 


0.42 
0.40 
0.37 


0.26 
0.25 
0.24 


0.1Q 
0.18 
0.18 


0.15 
0.14 
0.14 


0.12 
0.12 
0.11 


0.18 
0.17 
0.17 


0.14 
0.13 
0.13 


0.11 
0.11 
0.11 


0.49 
0.37 
032 
0.23 


0.28 
0.24 
0.22 
0.17 


0.20 
0.18 
0.16 
0.14 


0.15 
0.14 
0.13 
0.11 


0.12 
0.11 
0.11 
0.096 


0.19 
0.17 
0.16 
0.13 


0.14 
0.13 
0.12 
0.11 


0.12 
0.11 
0.10 
0.091 


0.32 
0.26 
0.24 
0.18 


0.21 
0.19 
0.17 
0.14 


0.16 
0.15 
0.14 
0.12 


0.13 
0.12 
0.11 
0.10 


0.11 
0.10 
0.097 
0.087 


0.15 
0.14 
0.13 
0.11 


0.12 
0.11 
0.11 
0.096 


0.10 
0.095 
0.092 
0.082 


0.40 
0.32 
0.26 
0.19 


0.25 
0.22 
0.19 
0.15 


0.18 
0.16. 
0.15 
0.12 


0.14 
0.13 
0.12 
0.10 


0.12 
0.11 
0.10 
0.09 


0.17 
0.15 
0.14 
0.12 


0.13 
0.12 
0.11 
0.10 


0.11 
0.10 
0.10 
0.08 


0.27 
0.23 
0.20 
0.16 


0.19 
0.17 
0.16 
0.13 


0.15 
0.14 
0.13 
0.11 


0.12 
0.11 
0.11 
0.09 


0.10 
0.097 
0.09 
0.08 


0.14 
0.13 
0.12 
0.10 


0.12 
0.11 
0.10 
0.09 


0.097 
0.091 
0.087 
0.077 


0.95 


0.39 


0.25 


0.18 


0.14 


0.23 


0.17 


0.13 


0.46 


0.27 


0.19 


0.15 


0.12 


0.18 


0.14 


0.11 



d These coefficients may be used with sufficient accuracy for wood lath and plaster, or plaster board and 
plaster ceilings. It is assumed that there is an air space between the under side of the roof deck and the 
upper side of the ceiling. 



115 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



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116 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 



TABLE 13. COEFFICIENTS OF TRANSMISSION (7) OF DOORS, WINDOWS, SKYLIGHTS 

AND GLASS WALLS 

Coefficients are based on a wind velocity of 15 mph, and are expressed in Biu per hour per square foot per 
degree Fahrenheit difference in temperature between the air inside and outside of the door, window, skylight or watt 

^ A . Windows and Skylights 

DESCRIPTION ' L" 



Single.- 

Double-- 
Triple.- 



0.45* 



B. Solid Wood Doors*>, 



NOMINAL 
THICKNESS 
INCHES 


ACTUAL 
THICKNESS U 
INCHES 


1 


% 


0.69 


1/4 


1K6 ; 0.59 


1% 


liKs 


0.52 


\% 


IN 


0.51 


2 


i 


0.46 


2Ji 


2N ; 0.38 


3 


25i 


0.33 



C. Glass Walls 



DESCRIPTION 


17 


Hollow glass tile wall, 6 x 6 x 2 in. thick blocks 
Wind velocity 15 mph, outside surface; still air, inside surface.-... 
Still air, outside and inside surface. 


0.60 
0.48 







See Heating, Ventilating and Air Conditioning, by Harding and Willard, revised edition, 1932. 

^Computed using C = 1.15 for wood; /i - 1.65 and/ = 6.0. 

"It is sufficiently accurate to use the same coefficient of transmission for doors containing thin wood 
panels as that of single panes of glass, namely, 1.13 Btu per hour per square foot per degree difference 
between inside and outside air temperatures. 

it is probable that the values of U for these two types of roofs will 
compare favorably. 

The thicknesses upon which the coefficients in Tables 3 to 13, inclusive, 
are based are as follows: 



Brick veneer 

Plaster and metal lath.. 



4 in. 
Kin. 



Plaster (on wood lath, plasterboard, rigid insulation, board 

form, or corkboard) 

Slate (roofing) 

Stucco on wire mesh reinforcing 

Tar and gravel or slag-surfaced built-up roofing. 

1-in. lumber (S-2-S) 

iH-in- lumber (S-2-S) 

2-in. lumber (S-2-S) _. 

2j^-in. lumber (S-2-S).. 

3-in. lumber (S-2-S). 

4-in. lumber (S-2-S)., 

Finish flooring (maple or oak)...., 

Solid brick walls are based on 4-in. hard brick (high density) and the 
remainder common brick (low density). Stucco is assumed to be 1-in. 
thick on masonry walls. Where metal lath and plaster are specified, the 
metal lath is neglected. 

117 




HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

The coefficients of transmission of the pitched roofs in Table 12 apply 
where the roof is over a heated attic or top floor so the heat passes directly 
through the roof structure including whatever finish is applied to the 
underside of the roof rafters. 

Combined Coefficients of Transmission 

If the attic is unheated, the roof structure and ceiling of the top floor 
must both be taken into consideration, and the combined coefficient of 
transmission determined. The formula for calculating the combined 
coefficient of transmission of a top floor ceiling, unheated attic space, and 
pitched roof, per square foot of ceiling area, is as follows: 

U T X /ce 

U - , tfce (6) 

Ur + ^r 

where 

U combined coefficient to be used with ceiling area. 
U r = coefficient of transmission of the roof. 
/ce = coefficient of transmission of the ceiling. 
n = the ratio of the area of the roof to the area of the ceiling. 

Stating the formula in terms of the total heat resistance of the ceiling 
and roof, 



In selecting the values to be used for U r and C/ce it should be noted 
that the under surface of the roof and the upper surface of the ceiling are 
more nearly equivalent to the boundary surfaces of an internal air space 
than they are to the external surfaces of a wall. It would be more nearly 
correct to use a value of 2.2 rather than the usual value of 1.65 as coef- 
ficients for these surfaces. In most cases this would make only a minor 
change in U. It should be noted that the over-all coefficient should be 
multiplied by the ceiling and not the roof area. 

If the unheated attic space between the roof and ceiling has no dormers, 
windows or vertical wall spaces the combined coefficients may be used 
for^determining the heat loss through the roof construction between the 
attic and top floor ceiling. If the unheated attic contains windows and 
vertical wall spaces these must be taken into consideration in calculating 
the roof area and also its coefficient Z7 r . In this case an approximate 
value of Z7 r may be obtained as the summation of the coefficient of each 
individual section such as the roof, vertical walls or windows times its 
percentage of total area. This coefficient may be used with reasonable 
accuracy in the above formulae. If, however, there are roof ventilators 
such that the attic air is substantially at outside temperature, then the 
roof should be neglected and only the coefficient for the 'top floor ceiling 
construction used. 

Basements and Unheated Rooms 

The heat loss through floors into basements and into unheated rooms 
kept closed may be computed by assuming a temperature for these rooms 

118 



CHAPTER 5. HEAT TRANSMISSION COEFFICIENTS AND TABLES 

of 32 F. Additional information on the inside and outside temperatures 
to be used in heat loss calculations is given in Chapter 7. 

REFERENCES 

Effects of Air Velocities on Surface Coefficients, by F. B. Rowley, A. B. Algren and 
J. L. Blackshaw (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930 } p. 123). 

Wind Velocity Gradients Near a Surface and Their Effect on Film Conductance, by 
F. C. Houghten and Paul McDermott (A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 301). 

Insulating Effect of Successive Air Spaces Bounded by Bright Metallic Surfaces, by 
L. W. Schad (A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 285). 

Conductivity of Concrete, by F. C. Houghten and Carl Gutberlet (A.S.H.V.E. 
TRANSACTIONS, Vol. 38, 1932, p. 47). 

Surface Coefficients as Affected by Direction of Wind, by F. B. Rowley and W. A. 
Eckley (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 33). 

Importance of Radiation in Heat Transfer Through Air Spaces, by E. R. Queer 
(A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 77). 

The Heat Conductivity of Wood at Climatic Temperature Differences, by F. B. 
Rowley (A.S.H.V.E. TRANSACTIONS, Vol. 39, 1933, p. 329). 

Insulating Value of Bright Metallic Surfaces, by F. B. Rowley (A.S.H.V.E. TRANS- 
ACTIONS, Vol. 40, 1934, p. 413). 

Thermal Properties of Concrete Construction, by F. B. Rowley, A. B. Algren and 
Clifford Carlson (A.S.H.V.E. TRANSACTIONS, Vol. 42, 1936, p. 33). 

Properties of Metal Foil as an Insulating Material, by J. L. Gregg (Refrigerating 
Engineering, May, 1932). 

Thermal Insulation with Aluminum Foil, by R. B. Mason (Industrial and Engineering 
Chemistry, March, 1933). 

Thermal Insulation of Buildings, Technical Paper No. 11 (American Architect, 
May, 1934). 

Thermal Properties of Concrete Construction, by F. B. Rowley, A. B. Algren and 
Robert Lander (A.S.H.V.E. JOURNAL SECTION, Heating, Piping and Air Conditioning, 
November, 1936, p. 621). 

Radiation and Convection Across Air Spaces in Frame Construction, by G. B. 
Wilkesand C. M. F. Peterson (A.S.H.V.E. JOURNAL SECTION, Heating, Piping and Air 
Conditioning, August, 1937, p. 505). 

Heat Insulation as Applied to Buildings and Structures, by E. A. Allcut, University 
of Toronto, 1934. 

House Insulation, Its Economies and Application, by Russell E. Backstrom (Report 
of the National Committee on Wood Utilization, United States Government Printing 
Office, 1931). 

Heat Transmission Through Building Materials, by F. B. Rowley and A. B. Algren, 
University of Minnesota Engineering Experiment Station Bulletin No. 8. 

Calculation of Heat Transmission, by Margaret Fishenden and Owen A. Saunders. 

Heating, Ventilating and Air Conditioning, by Harding and Willard, Revised Edition, 
1932. 

Heat Transmission, by W. H. McAdams. 
Industrial Heat Transfer, by Shack. 

PROBLEMS IN PRACTICE 

1 What is the coefficient U and how is it applied? 

The coefficient U is the heat loss through walls, ceilings, and floors and the value depends 
upon the construction and material, expressed in Btu per hour per square foot per degree 
difference in temperature between the inside and outside. To determine the total heat 
loss, multiply U for each material by the square feet of surface and the temperature 
difference. 

119 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

2 Find the value of U for a 6-in. concrete wall with plaster on metal lath 
attached to 2-in. furring strips with flanged J^-in. blanket insulation. 

0.23 (Table 3, Wall 12L). 

3 A wall is built with two layers of J^-in. insulating material spaced 1 in. 
apart; the air space is lined on one side with bright aluminum foil; mean 
temperature is 40 F; still air on both sides of wall; k for insulating material 
is 0.34. Calculate the value of U. 

fl = 1.65; / = 1.65; a = 0.46 

. l ft 397 
" = 6 ' 327 



U - -J- - 0.158 

4 What is the inside surface temperature of a 6-in. solid concrete wall? 
Inside ah*, 70 F; outside air, -20 F with 15 mph wind. 

The temperature drop from point to point through a wall is directly proportional to the 
heat resistance. 

fl = 1.65; k for concrete = 12.62 ;/ = 6.0 
Over-all resistance R = + + JL . 1 



Temperature drop, inside air to surface 1.65 
Temperature drop, air to air 1.27 

90 

Temperature drop, inside air to surface = ., nfy , _ g = 43 

L.( X l.oo 

70 43 = 27 F, inside surface temperature of wall. 

5 How many inches of insulating material having a conductivity of 0.30 
would be required, for the wall of Question 4, to raise the inside surface tem- 
perature to 60 F? 

Temperature drop, air to inside surface = 10 F; temperature drop, inside surface to out- 
side air 80 F. Therefore, the heat resistance from inside wall surface to outside air 

must be eight times that from inside air to inside wall surface, or 8 X -rir- = 4.85. The 

1.65 
resistance for added material is, therefore, 



485 - TO + = 4 - 19 

4.19 X 0.30 - 1.25 in. of insulation. 

6 f, - n unheated attic space in a residence has an equivalent pitched roof area 
of 1560 sq ft and a ceiling area of 1200 sq ft. If 15 per cent of the roof area is 
composed of vertical wall spaces having a value of U = 0.52, determine the 
total heat loss per hour through the ceiling and roof for a temperature dif- 
ference of 85 F, if U = 0.46 for the roof and U = 0.38 for the ceiling. 

An approximate value of U for the roof is equivalent to the summation of coefficients 
tor each individual section times its percentage of total area. 

UT = (0.52 X 0.15) -f- (0.46 X 0.85) = 0.47. 
Ratio of roof area, to ceiling = 1560 -f- 1200 = 1.3. 
Substituting in Formula 6: 

0.47 X 0.38 



H = A U ft - / ) = 1200 X 0.235 X 85 = 23,900 Btu per hour. 

120 



Chapter 6 

AIR LEAKAGE 

Nature of Air Infiltration, Infiltration Through Walls, Window 

Leakage, Door Leakage, Selection of Wind Velocity, Crack 

Length used for Computations, Multi-Story Buildings, Heat 

Equivalent of Air Infiltration 

AIR leakage losses are those resulting from the displacement of heated 
air in a building by unheated outside air, the interchange taking 
place through various apertures in the building, such as cracks around 
doors and windows, fireplaces and chimneys. This leakage of air must be 
considered in heating and cooling calculations. (See Chapters 7 and 8.) 

NATUBE OF Am INFILTRATION 

The natural movement of air through building construction is due to 
two causes. One is the pressure exerted by the wind; the other is the 
difference in density of outside and inside air because of differences in 
temperature. 

The wind causes a pressure to be exerted on one or two sides of a 
building. As a result, air comes into the building on the windward side 
through cracks or porous construction, and a similar quantity of air 
leaves on the leeward side through like openings. In general the resis- 
tance to air movement is similar on the windward to that on the leeward 
side. This causes a building up of pressure within the building and a 
lesser air leakage than that experienced in single wa.ll tests as determined 
in the laboratory. It is assumed that actual building leakages owing to 
this building up of pressure will be 80 per cent of laboratory test values. 
While there are cases where this is not true, tests in actual buildings 
substantiate the factor for the general case. Tests on mechanically 
ventilated classrooms of average construction have shown that air 
infiltration acts quite independently of the planned air supply. Accor- 
dingly, the heating or cooling load owing to air infiltration from natural 
causes should be considered in addition to the ventilating load. 

The air exchange owing to temperature difference, inside to outside, is 
not appreciable in low buildings. In tall, single story buildings with 
openings near the ground level and near the ceiling, this loss must be 
considered. Also in multi-story buildings it is a large item unless the 
sealing between various floors and rooms is quite perfect. This tempera- 
ture effect is a chimney action, causing air to enter through openings at 
lower levels and to leave at higher levels. 

A complete study of all of the factors involved in air movement through 
building constructions would be very complex* Some of the complicating 

121 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

factors are: the variations in wind velocity and direction; the exposure of 
the building with respect to air leakage openings and with ^ respect ^ to 
adjoining buildings; the variations in outside temperatures asjnfluencing 
the chimney effect; the relative area and resistance of openings on the 
windward and leeward sides and on the lower floors and on the upper 
floors; the influence of a planned air supply and the related outlet vents; 
and the variation from the average of individual building units. A study 
of infiltration points to the need for care in the obtaining of good building 
construction, or unnecessarily large heat losses will result. 



INFILTRATION THROUGH WALLS 

Table 1 gives data on infiltration through brick and frame walls. The 
brick walls listed in this table are walls which show poor workmanship 
and which are constructed of porous brick and lime mortar. For good 
workmanship, the leakage through hard brick walls with cement-lime 
mortar does not exceed one-third the values given. These tests indicate 
that plastering reduces the leakage by about 96 per cent; a heavy coat of 
cold water paint, 50 per cent; and 3 coats of oil paint carefully applied, 
28 per cent. The infiltration through walls ranges from 6 to 25 per cent 
of that through windows and doors in a 10-story office building, with 
imperfect sealing of plaster at the baseboards of the rooms. With perfect 
sealing the range is from 0.5 to 2.7 per cent or a practically negligible 
quantity, which indicates the importance of good workmanship in proper 
sealing at the baseboard. It will be noted from Table 1, that the in- 
filtration through properly plastered walls can be neglected. 

The value of building paper when applied between sheathing and 
shingles is indicated by Fig. 1, which represents the effect on outside 
construction only, without lath and plaster. The effectiveness of plaster 
properly applied is no justification for the use of low grade building paper 
or of the poor construction of the wall containing it. Not only is it 

TABLE 1. INFILTRATION THROUGH WALLS** 

Expressed in cubic feet per square foot per hour 



TTPB OF WALL 


WIND VKLOCITT, MIUBS EBB HOUB 


5 


10 


15 


20 


25 


30 


8Ji in. Brick TOL^gj-j- 


1.75 
0.017 


4.20 
0.037 


7.85 
0.066 


12.2 
0.107 


18.6 
0.161 


22.9 
0.236 


i *> T> j-t \\7 IT / i*ain. __. 


1.44 
0.005 


3.92 
0.013 


7.48 
0.025 


11.6 
0.043 


16.3 
0.067 


21.2 
0.097 


13 in. Bnck Wall 1^^^^.. 


Frame Wall, with lath and plaster^ 


0.03 


0.07 


0.13 


0.18 


0.23 


0.26 



_ The values given in this table are 20 per cent less than test values to allow for building up of pressure 
in rooms and are based on test data reported in the papers listed at the end of this chapter. 

BeVd * Ming P8intcd f Cedar shingles ' sheathi *g. building paper, wood lath and 



122 



CHAPTER 6. AIR LEAKAGE 



0.45 




20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 
INFILTRATION, C FH PER SQ FT OF WALL 

FIG. 1. INFILTRATION THROUGH VARIOUS TYPES OF SHINGLE CONSTRUCTION 

difficult to secure and maintain the full effectiveness of the plaster but 
also it is highly desirable to have two points of high resistance to air flow 
with an air space between them. 

The amount of infiltration that may be expected through simple walls 
used in farm and other shelter buildings, is shown in Fig. 2. The infil- 
tration indicated in Figs. 1 and 2 is that determined in the laboratory and 
should be multiplied by the factor 0.80 to give proper working values. 



<r 0.40 - - - 

g ::: 




140 160 180 200 220 



INFILTRATION, C FH PER SQ FT OF WALL 



FIG. 2. INFILTRATION THROUGH SINGLE SURFACE WALLS USED IN FARM AND 
OTHER SHELTER BUILDINGS 

123 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



WINDOW LEAKAGE 

The amount of infiltration for various types of windows is given in 
Table 2. The fit of double-hung wood windows is determined by crack 
and clearance as illustrated in Fig. 3. The length of the perimeter opening 
or crack for a double-hung window is equal to three times the width plus 
two times the height, or in other words, it is the outer sash ^ perimeter 
length plus the meeting rail length. Values of leakage shown in Table 2 
for the average double-hung wood window were determined by setting 
the average measured crack and clearance found in a field survey of a 
large number of windows on nine windows tested in the laboratory. In 
addition, the table gives figures for a poorly fitted window. All of the 
figures for double-hung wood windows are for the unlocked condition. 
Just how a window is closed, or fits when it is closed, has considerable 
influence on the leakage. The leakage will be high if the sash are short, 
if the meeting rail members are warped, or if the frame and sash are not 




FIG. 3. DIAGRAM ILLUSTRATING CRACK AND CLEARANCE 

fitted squarely to each other. It is possible to have a window with 
approximately the average crack and clearance that will have a leakage 
at least double that of the figures shown. Values for the average double- 
hung wood window in Table 2 are considered to be easily obtainable 
figures provided the workmanship on the window is good. Should it be 
known that the windows under consideration are poorly fitted, the larger 
leakage values should be used. Locking a window generally decreases its 
leakage, but in some cases may push the meeting rail members apart and 
increase the leakage. On windows with large clearances, locking will 
usually reduce the leakage. 

Wood casement windows may be assumed to have the same unit 
leakage as for the average double-hung wood window when properly 
fitted. ^ Locking, a normal operation in the closing of this type of window, 
maintains the crack at a low value. 

For metal pivoted sash, the length of crack is the total perimeter of the 
movable or ventilating sections. Frame leakage on steel windows may be 
neglected when they are properly grouted with cement mortar into brick 
work or concrete. When they are not properly sealed, the linear feet of 
sash section in contact with steel work at mullions should be figured at 
25 per cent of the values for industrial pivoted windows as given in 
Table 2. 

124 



CHAPTER 6. AIR LEAKAGE 



H WINDOW. IN. OF WATER 

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45.69 

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35,40 s . 
28.90 g 

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$ 
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B 
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-Storm sash, suspend 
Storm sash, fastened 
With four turn button 
-Same as C with wool 
weatherstrip applied 
to storm sash 


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50 100 150 200 250 300 
INFILTRATION, CFH PER FOOT OF CRACK 



FIG. 4. INFILTRATION THROUGH SASH PERIMETER OF WINDOW WITH AND WITHOUT 
STORM SASH J^-IN. CRACK AND J^-IN. CLEARANCE 

Leakage values for storm sash are given in Figs. 4 and 5. When storm 
sash are applied to well fitted windows, very little reduction in infiltration 
is secured, but the application of the sash does give an air space which 
reduces the heat transmission and helps prevent the frosting of the 
windows. When storm sash are applied to poorly fitted windows, a 
reduction in leakage of 50 per cent may be secured. 



W, IN. OF WATER 
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DO K 


















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^ WIND VELOCITY, MILES PER HOUR 


























































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B- Storm sash, s 
C- Storm sash, 1 
with four tun 


isash 
uspend 
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s 
































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100 150 200 250 300 350 400 4 
1NF1LTRATION.C F H PER FOOT OF CRACK 



FIG. 5. INFILTRATION THROUGH SASH PERIMETER OF WINDOW WITH AND WITHOUT 
STORM SASH H-m. CRACK AND J^-IN. CLEARANCE 

125 



HEATING VENTIIIATING AIR CONDITIONING GUIDE 1938 



TABLE 2, INFILTRATION THROUGH WINDOWS 

Expressed in Cubic Feet per Foot of Crack per Hour& 



Tr? OF WINDOW 



REMARKS 





5 


10 


15 


20 


25 


30 


Double-Hung 
Wood Sash 
Windows 
(Unlocked) 


1 Around frame in masonry wall not calkedb 


3.3 


8.2 


14.0 


20.2 


27.2 


34.6 


Around frame In masonry wall calkedb 


0.5 


1.5 


2.6 


3.8 


4.8 


5.8 


Around frame in wood frame construction^ 


2.2 


6.2 


10.8 


16.6 


23.0 


30.3 


Total for average window, non-weather- 
stripped, He-in. crack and ?&-in. clearancec. 
Includes wood frame leakage^ 


6.6 


21.4 


39.3 


59.3 


80.0 


103.7 


Ditto, weatherstrippedd 


4.3 


15.5 


23.6 


35.5 


48.6 


63.4 




Total for poorly fitted window, non- weather- 
stripped, 5^-in. crack and ?-m. clearance.* 
Includes wood frame leakaged 


26.9 


69.0 


110.5 


153.9 


199.2 


249.4 


Ditto, weatlierstrippedd 


5.9 


18.9 


34.1 


51.4 


70.5 


91.5 


Double-Hung 
Metal 
Windows* 


Non-weatierstripped, locked 
Non-weatherstripped, unlocked. 
Weatherstripped, unlocked 


20 
20 
6 


45 
47 
19 


70 
74 
32 


96 
104 
46 


125 
137 
60 


154 

170 
76 


Rolled 
Section 
Steel 

Sash 
Windows^ 


Industrial pivoteds, J4-in. crack. 
Architectural projected, J^-in. crack** 
Architectural projected, %-in. crackh . 


52 
15 

20 
6 
14 

3 

8 


108 
36 
52 
18 
32 

10 
24 


176 
62 
88 
33 
52 

18 
38 


244 
86 
116 
47 
76 

26 
54 


304 
112 
152 
60 
100 

36 

72 


372 
139 
182 

74 
128 

48 
92 


Residential casement, l^-in. crack* 

Residential casement, J^-in. crack* 
Heavy casement section, projected, J^-in. 

cracki . 


Heavy casement section, projected J^-in. 

eraeki 




Hollow Metal, vertically pivoted window f 


30 


88 


145 


186 


221 


242 



WIND VELOCITY, MILES PIB HOUR 



aThe values given In this table are 20 per cent less than test values to allow for building up of pressure in 
rooms, and are based on test data reported in the papers listed at the end of this chapter. 

f fcThe values given for frame leakage are per foot of sash perimeter as determined for double-hung wood 
windows. Some of the frame leakage in masonry walls originates in the brick wall itself and cannot be 
prevented by calking. For the additional reason that calking is not done perfectly and deteriorates with 
tome, it is considered advisable to choose the masonry frame leakage values for calked frames as the average 
determined by the calked and not-calked tests. 

cThe fit of the average double-hung wood window was determined as }-in. crack and ?&-in. clearance by 
measurements on approximately 600 windows under heating season conditions. 

dThe values given are the totals for the window opening per foot of sash perimeter and include frame 
leakage and so-called elsewhere leakage. The frame leakage values included are for wood frame construction 
but apply as well to masonry construction assuming a 50 per cent efficiency of frame calking. 

A %-in. crack and clearance represents a poorly fitted window, much poorer than average. 

^Windows tested in place in building. 

^Industrial pivoted, window generally used in industrial buildings. Ventilators horizontally pivoted 
at center or slightly above, lower part swinging out. 

_ ^Architectural projected made of same sections as industrial pivoted except that outside framing member 
is heavier, and refinements in weathering and hardware. Used in semi-monumental buildings such as 
schools. Ventilators swing in or out and are balanced on side arms. J^-in. crack is obtainable in the best 
practice of manufacture and installation, Jfl-in. crack considered to represent average practice. 
S f ** ^ e ^ esi n a nd section shapes as so-called heavy section casement but of lighter weight. ki-n. crack 
practice* m P 1 "^^ <> f manufacture and installation, J^-in. crack considered to represent average 



u+ - - ^i " . se tions - Ventilators swing in or out and stay set at any degree of opening. J^-in. crack 
is obtainable m the best practice of manufacture and installation, fc-in. crack considered to represent 
average practice. 

With reasonable care in installation leakage at contacts where windows are attached to steel frame- 
work and at muUions is negligible. With &-in. crack, representing poor installation, leakage at contact 
Sndow? i^thfSbk 18 * ne " third ' and at mullion s about one-sixth of that given for industrial pivoted 

126 



CHAPTER 6. AIR LEAKAGE 



DOO1 LEAKAGE 

Doors vary greatly in fit because of their "large size and tendency to 
warp. For a well fitted door, the leakage values for a poorly fitted double- 
hung'wood window may be used. If poorly fitted, twice this figure should 
be used. If weatherstripped, the values may be reduced one-half. A 
single door which is frequently opened, such as might be found in a store, 
should have a value applied which is three times that for a well fitted 
door. This extra allowance is for opening and closing losses and is kept 
from being greater by the fact that doors are not used as much in the 
coldest and windiest weather. 

The infiltration rate through swinging and revolving doors is generally 
a matter of judgment by the engineer making cooling load determinations 
and in the absence of adequate research data the values given in Table 3 
represent current engineering practice. These values are based on the 
average number of persons in a room at a specified time, which may also 
be the same occupancy assumed for determining the outside ventilation 
requirements outlined in Chapters 3 and 8. 

TABLE 3. INFILTRATION THROUGH OUTSIDE DOORS FOR COOLING LOADS & 
Expressed in Cubic Feet per Minute per Person in Room 



APPLICATION 


PA.IH 36 IN. SWINGING 
DOOKS, SINGLE 

ENTRANCEb 


"D^r-ilr ' 


7.5 
4.5 
7.0 
6.0 
25.0 
8.0 
2.5 
7.0 
2.5 
3.5 
5.0 
3.5 
3.0 
2.0 
2.5 
2.5 
3.5 

Tin? tvne. 




Barber Shop 












Drug Store - 


Furrier 




A/To.'o QVirvn - " 


Men s onop 

/"X-GC/N/i - - 




Office Building 


Public Building 


Restaurant - 

Ql-n-id QfTvr*=- * * 





aFor doors located m omy one wa.u <JL wiicxc v.^**, ^ - --------- - : 

Westibules with double pair swinging doors, infiltration may be assumed 75 per cent of swmgmg 

on for 72 in. revolving doors may be assumed 60 per cent of swinging door values. 



SELECTION OF WIND VELOCITY 

Although all authorities do not agree upon the value of the wind veloc- 
ity that should be chosen for any given locality, it is common engineering 
practice to use the average wind velocity during the three coldest months 
of the year. Until this point is definitely established the practice of 
using average values will be followed. Average wind velocities for the 
monlhs of December, January and February for various cities in the 
United States and Canada are given in Table 2, Chapter /. 



127 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

In considering both the transmission and infiltration losses, the more 
exact procedure would be to select the outside temperature and the wind 
velocity corresponding thereto, based on Weather Bureau records, which 
would result in the maximum heat demand. Since the proportion of 
transmission and infiltration losses varies with the construction and is 
different for every building, the proper combination of temperature and 
wind velocity to be selected would be different for every type of building, 
even in the same locality. Furthermore, such a procedure would necessi- 
tate a laborious cut-and-try process in every case in order to determine 
the worst combination of conditions for the building under consideration. 
It would also be necessary to consider heat lag due to heat capacity in the 
case of heavy masonry walls, and other factors, to arrive at the most 
accurate solution of the problem. Although heat capacity should be con- 
sidered wherever possible, it is seldom possible to accurately determine the 
worst combination of outside temperature and wind velocity for a given 
building and locality. The usual procedure, as explained in Chapter 7, 
is to select an outside temperature which is not more than 15 F above 
the lowest recorded, and the average wind velocity during the months 
of December, January and February. 

The direction of prevailing winds may usually be included within an 
angle of about 90 deg. The windows that are to be figured for prevailing 
and non-prevailing winds will ordinarily each occupy about one-half the 
perimeter of the structure, the proportion varying to a considerable extent 
with the plan of the structure. (See discussion of wind movement in 
Chapter 36.) 

CRACK LENGTH USED FOR COMPUTATIONS 

In no case should the amount of crack used for computation be less 
than half of the total crack in the outside walls of the room. Thus, in a 
room with one exposed wall, take all the crack; with two exposed walls, 
take the wall having the most crack; and with three or four exposed walls, 
take the wall having the most crack; but in no case take less than half the 
total crack. For a building having no partitions, whatever wind enters 
through the cracks on the windward side must leave through the cracks 
on the leeward side. Therefore, take one-half the total crack for com- 
puting each side and end of the building. 

The amount of air leakage is sometimes roughly estimated by assuming 
a certain number of air changes per hour for each room, the number of 
changes assumed being dependent upon the type, use and location of the 
room, as indicated in Table 4. This method may be used to advantage as 
a check on the calculations made in the more exact manner. 

MULTI-STORY BUILDINGS 

In tall buildings, infiltration may be considerably influenced by tem- 
perature difference or chimney effect which will operate to produce a 
head that will add to the effect of the wind at lower levels and subtract 
from it at higher levels. On the other hand, the wind velocity at lower 
levels may be somewhat^ abated by surrounding obstructions. Further- 
more,^ the chimney effect is reduced in multi-story buildings by the partial 
isolation of floors preventing free upward movement, so that wind and 

128 



CHAPTER 6. AIR LEAKAGE 



TABLE 4. AIR CHANGES TAKING PLACE UNDER AVERAGE CONDITIONS EXCLUSIVE 
OF AIR PROVIDED FOR VENTILATION 



KIND OP ROOM OB BUILDING 



NUMBER or AIR CHANGM 

TAKING PLACE 

PER Horn 



Rooms, 1 side exposed I 1 

Rooms, 2 sides exposed i 1J 

Rooms, 3 sides exposed 2 

Rooms, 4 sides exposed 2 

Rooms with no windows or outside doors._ 



Entrance Halls 
Reception Halls 



2 to 3 
2 



Living Rooms. ........................................................................... i 1 to 2 



Dining Rooms , 

Bath Rooms 

Drug Stores 

Clothing Stores 

Churches, Factories, Lofts, etc.. 



Ito2 

2 
2 to 3 

1 



temperature difference may seldom cooperate to the fullest extent. 
Making the rough assumption that the neutral zone is located at mid- 
height of a building, and that the temperature difference is 70 F, the 
following formulae may be used to determine an equivalent wind velocity 
to be used in connection with Tables 1 and 2 that will allow for both wind 
velocity and temperature difference: 

- 1.75 a (1) 



+ 1.75 b (2) 

where 

Mt equivalent wind velocity to be used in conjunction with Tables 1 and 2. 
j|f = wind velocity upon which infiltration would be determined if tem- 
perature difference were disregarded. 
a = distance of windows under consideration from mid-height of building 

if above mid-height. 
b distance if below mid-height. 

The coefficient 1.75 allows for about one-half the temperature difference head. 

For buildings of unusual height, Equation 1 would indicate negative 
infiltration at the highest stories, which condition may, at times, actually 
exist. 

Sealing of Vertical Openings 

In tall, multi-story buildings, every effort should be made to seal off 
vertical openings such as stair-wells and elevator shafts from the re- 
mainder of the building. Stair-wells should be equipped with self-closing 
doors, and in exceptionally high buildings, should be closed off into 
sections of not over 10 floors each. Plaster cracks should be filled. 
Elevator enclosures should be tight and solid doors should be used. 

If the sealing of the vertical openings is made effective, no allowance 
need be made for the chimney effect. Instead, the greater^wind move- 
ment at the high altitudes makes it advisable to install additional heating 
surface on the upper floors above the level of neighboring buildings, this 
additional surface being increased as the height is increased. One 

129 



HEATING VENTILATING Am CONDITIONING GUIDE 1938 

arbitrary rule is to increase the heating surface on floors above neighboring 
buildings by an amount ranging from 5 per cent to 20 per cent. This extra 
heating surface is required only on the windward side and^on windy days, 
and hence automatic temperature control is especially desirable with such 
installations. 

In stair- wells that are open through many floor levels although closed 
off from the remainder of each floor by doors and partitions, the strati- 
fication of air makes it advisable to increase the amount of heating surface 
at the lower levels and to decrease the amount at higher levels even to the 
point of omitting all heating surface on the top several floor levels. One 
rule is to calculate the heating surface of the entire stair-well in the usual 
way and to place 50 per cent of this in the bottom third, the normal 
amount in the middle third and the balance in the top third. 

HEAT EQUIVALENT OF AIR INFILTRATION 
Sensible Heat Loss 

The heat required to warm cold outside air, which enters a room by 
infiltration, to the temperature of the room is given by the equation: 

H B = 0.24 Q d (ti - t ) (3) 

where 

H s = heat required to raise temperature of air leaking into building from t to t{ 

Btu per hour. 
0.24 = specific heat of air. 

Q = volume of outside air entering building, cubic feet per hour. 
d = density of air at temperature t , pounds per cubic foot. 
t\ room air temperature, degrees Fahrenheit. 
t ~ outside air temperature, degrees Fahrenheit. 

Latent Heat Loss 

When it is intended to add moisture to air leaking into a room for the 
maintenance of proper winter comfort conditions, it is necessary to 
determine the heat equivalent to evaporate the required amount of water 
vapor, which may be calculated by the equation : 



7000 
where 

Hi = heat required to increase moisture content of air leaking into building from 
Mo to Mi, Btu per hour. 

Q volume of outside air entering building, cubic feet per hour. 

d = density of air at temperature ti, pounds per cubic foot. 
Mi vapor density of inside air, grains per pound of dry air. 
Mo = vapor density of outside air, grains per pound of dry air. 

L = latent heat of vapor at MI, Btu per pound. 

It is sufficiently accurate to use d = 0.075 Ib, in which case equation 3 
reduces to 5 and if the latent heat of vapor is assumed for general condi- 
tions as 1060 Btu per pound equation 4 reduces to 6. 

H s = 0.018 Q (ti - to) (5) 

fli = 0.0114 Q (Mi - Mo) (6) 

While a heating reserve must be provided to warm inleaking air on 
the windward side of a building, this does not necessarily mean that the 

130 



CHAPTER 6. AIR LEAKAGE 



heating plant must be provided with a reserve capacity, since the inleaking 
air, warmed at once by adequate heating surface in exposed rooms, will 
move transversely and upwardly through the building, thus relieving 
other radiators of a^part of their load. The actual loss of heat of a building 
caused by infiltration is not to be confused with the necessity for pro- 
viding additional heating capacity for a given space. Infiltration is a 
disturbing factor in the heating of a building, and its maximum effect 
(maximum in the sense of an average of wind velocity peaks during the 
heating season above some reasonably chosen minimum)must be met 
by a properly distributed reserve of heating capacity, which reserve, how- 
ever, is not in use at all places at the same time, nor in any one place at 

all times. 

REFERENCES 

Air Leakage, by F. C. Houghten and C. C. Schrader (A.S.H.V.E. TRANSACTIONS, 
Vol. 30, 1924, p. 105). 

Air Leakage around Window Openings, by C. C. Schrader (A.S.H.V.E. TRANSACTIONS, 
Vol. 30, 1924, p. 313). 

Neutral Zone in Ventilating, by J. E. Emswiler (A.S.H.V.E. TRANSACTIONS, Vol. 32, 
1926, p. 59). 

Infiltration through Plastered and Unplastered Brick Walls, by F. C. Houghten and 
Margaret Ingels (A.S.H.V.E. TRANSACTIONS, Vol. 33, 1927, p. 377). 

Effect of Frame Calking and Storm Sash on Infiltration around and through Windows, 
by W. M. Richtmann and C. Braatz (A.S.H.V.E. TRANSACTIONS, Vol. 34, 1928 T p. 547). 

Air Leakage on Metal Windows in a Modern Office Building, by F. C. Houghten and 
M. E. O'Connell (A.S.H.V.E. TRANSACTIONS, Vol. 34, 1928, p. 321). 

The Weathertightness of Rolled Section Steel Windows, by J. E. Emswiler and 
W. C. Randall (A.S.H.V.E. TRANSACTIONS, Vol. 34, 1928, p. 527). 

Air Leakage through a Pivoted Metal Window, by F. C. Houghten and M. E. 
O'Connell (A.S.H.V.E. TRANSACTIONS, Vol. 34, 1928, p. 519). 

Air Infiltration through Various Types of Brick Wall Construction, by G. L. Larson, 
D. W. Nelson and C. Braatz (A.S.H.V.E. TRANSACTIONS, Vol. 35, 1929, p. 183). 

Pressure Differences across Windows in Relation to W : ind Velocity, by J. E. Emswiler 
and W. C. Randall (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 83). 

Air Infiltration Through Various Types of Wood Frame Construction, by G. L. 
Larson, D. W. Nelson and C. Braatz (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 99). 

Air Infiltration Through Double-Hung Wood Windows, by G. L. Larson, D. W. 
Nelson and R. W. Kubasta (A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 571). 

Flue Action in Tall Buildings, by H. L. Alt (Heating, Piping and Air Conditioning, 
May, 1932). 

Air Infiltration Through Steel Framed Windows, by D. 0. Rusk, V. H. Cherry and 
L. Boelter (Heating, Piping and Air Conditioning, October, 1932). 

Investigation of Air Outlets in Class Room Ventilation, by G. L. Larson, D. W. 
Nelson and R. W. Kubasta (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 463). 

Influence of Stack Effect on the Heat Loss in Tall Buildings, by Axel Marin (A.S.H. 
V.E. TRANSACTIONS, Vol. 40, 1934, p. 377). 

Wind Velocities Near a Building and Their Effect on Heat Loss, by F. C. Houghten, 
J. L. Blackshaw, and Carl Gutberlet (A.S.H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 387). 

Fuel Saving Resulting from the Use of Storm Windows and Doors, by A. P. Kratz and 
S. Konzo (A.S.H.V.E. TRANSACTIONS, Vol. 42, 1936, p. 87). 

The Infiltration Problem of Multiple Entrances, by A. M. Simpson and K. B. Atkinson 
(A.S.H.V.E. JOURNAL SECTION, Heating, Piping and Air Conditioning, June, 1936). 

Infiltration Characteristics of Entrance Doors, by A. M. Simpson (Refrigerating 
Engineering, June, 1936). 

Heating Requirements of an Office Building as Influenced by the Stack Effect, by 
F. C. Houghten and Carl Gutberlet (A.S.H.V.E. JOURNAL SECTION, Heating, Piping 
and Air Conditioning, July, 1937). 

131 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

PROBLEMS IN PRACTICE 

1 What two natural forces cause infiltration? 

c. Wind causes^ pressure to be exerted on one or two sides of a building with consequent 
movement of air through openings. 

i>. Temperature difference inside to outside causes a difference in density with con- 
sequent entrance of air at lower openings and exit of air at higher openings. 

2 What is the neutral zone as applied to infiltration in buildings? 

Due to temperature difference inside air tends to flow out of openings near the top of 
the building and is replaced by outside air coming in at lower openings. At some height 
no flow occurs in or out. This is referred to as the neutral zone and often is taken at the 
mid-height of the building but may be higher or lower than this depending on several 
factors. 

3 In what type of structure is infiltration due to temperature difference 
of importance? 

In tall open buildings, in multi-story buildings inadequately sealed between floors and 
in stair- wells for multi-story buildings the temperature difference effect is important. 

4 What procedure is sometimes used to compensate for this temperature 
or chimney effect in stair-wells? 

One rulejs to place 50 percent of the calculated radiation in the bottom third, the normal 
amount in the middle third and the remainder in the top third. 

5 Why is it customary to apply a correction factor to laboratory values before 
calculating infiltration in buildings? 

Most, if not all, laboratory values have been determined by exerting a certain wind 
pressure across a single thickness of building construction. In actual building con- 
struction the pressure drop due to wind velocity takes place in two steps, one through 
the windward and the other through the leeward wall. Tests indicate that the leakage 
in actual construction will be about 80 per cent of laboratory values and therefore this 
factor has been applied in making up the tables in this chapter. The curves represent 
laboratory data as taken with no correction applied. 

6 Is infiltration through walls of importance? 

In the case of compound walls of good construction the heat loss due to infiltration is 
usually negligibly low. In the case of single thickness walls without building paper 
properly applied, the heat loss due to air leakage may be very high. 

7 How are the wind velocities and outside temperatures selected for infil- 
tration calculations in heating? 

It is common practice to take the average wind velocity for the three coldest months 
and the temperature as 15 F above the coldest recorded by the Weather Bureau during 
the proceeding 10 years. 

80 Show the probable combined effects of infiltration due to temperature 
difference and wind velocity on the ground floor and on the 15th floor of a 20- 
story building 200 ft high with a 12 mph wind blowing. 

At the ground floor the effective velocity is increased to: 



K e = V12 2 + 1.75 X 100 = 17.8 mph 
At the 15th floor level it would be reduced to: 

Me = V12 2 - 1.75 X 50 = 7.5 mph 
9 What is the value of storm sash in reducing infiltration? 

The reduction depends on the relative fit of the window and the storm sash. Fig. 4 
indicates for storm sash buttoned on a reduction at 20 mph from about 52 cfh per foot 
of crack to 42 cfh. Fig. 5 indicates a reduction for a storm sash buttoned over a loosely 
fitted window from 185 to 90 cfh. 

132 



Chapter 7 

HEATING LOAD 

Heat Demand Design Factors, Method of Procedure, Inside 
and Outside Temperatures, Wind Velocity Effects, Auxiliary 
Heat Sources, Wall Condensation, Heat Loss Computation 

TO design any system of heating, the maximum probable heat^demand 
must be accurately estimated in order that the apparatus installed 
shall be capable of maintaining the desired temperature at all times. The 
factors which govern this maximum heat demand most of which are 
seldom, if ever, in equilibrium include the following: 

1. Outside temperature. 1 

2. Rain or snow. Outside Conditions 

3. Sunshine or cloudiness. (The Weather) 

4. Wind velocity. J 



5. Heat transmission of exposed parts of building. 

6. Infiltration of air through cracks, crevices and 

open doors and windows. 

7. Heat capacity of materials. 

8. Rate of absorption of solar radiation by exposed 

materials. 

9. Inside temperatures. 

10. Stratification of air. 

11. Type of heating system. 

12. Ventilation requirements. 

13. Period and nature of^ occupancy. 

14. Temperature regulation. 



Building 
Construction 



Inside 
Conditions 



The inside conditions vary from time to time, the physical properties of 
the building construction may change with age, and the outside conditions 
are changing constantly. Just what the worst combination of all of these 
variable factors is likely to be in any particular case is. therefore con- 
iectural. Because of the nature of the problem, extreme precision in 
estimating heat losses at any time, while desirable, is hard of attainment. 

The procedure to be followed in determining the heat loss from any 
building can be divided into seven consecutive steps, as follows: 

1. Determine on the inside air temperature, at the breathing line or the i 30-in. line, 
which is to be maintained in the building during the coldest weather. (See Table 1.) ^ 

2. Determine on an outside air temperature for design purposes, t^ WfP 1 ? 1 ^; 
temperatures recorded in the locality in question, which will provide for all but the 
most severe weather conditions. Such conditions as may exist for only a few .consecu- 
tive hours are readily taken care of by the heat capacity of the building itself. 



(See Table 2.) 

133 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



3. Select or compute the heat transmission coefficients for outside walls and glass; 
also for inside walls, floors, or top-floor ceilings, if these are next to unheated space; 
include roof if next to heated space. (See Chapter 5.) 

4. Measure up net outside wall, glass and roof next to heated spaces, as well as any 
cold walls, floors or ceilings next to unheated space. Such measurements are made from 
building plans, or from tie actual building. 

5. Compute the heat transmission losses for each kind of wall, glass, floor, ceiling 
and roof in the building by multiplying the heat transmission coefficient in each case 
by the area of the surface in square feet and the temperature difference between the 
inside and outside air. (See Items 1 and 2.) 

6. Select unit values and compute the heat equivalent of the infiltration of cold air 
taking place around outside doors and windows. These unit values depend on the kind or 
width of crack and wind velocity, and when multiplied by the length of crack and the 
temperature difference between the inside and outside air, the result expresses the heat 
required to warm up the cold air leaking into the building per hour. (See Chapter 6.) 

7. The sum of the heat losses by transmission (Item 5) through the outside wall and 
glass, as well as through any cold floors, ceilings or roof, plus the heat equivalent (Item 6) 
of the cold air entering by infiltration represents the total heat loss equivalent for any 
building. 

Item 7 represents the heat losses after the building is heated and under 
stable operating conditions in coldest weather. Additional heat is 
required for raising the temperature of the air, the building materials and 
the material contents of the building to the specified standard inside 
temperature. 

The rate at which this additional heat is required depends upon the 
heat capacity of the structure and its material contents and upon the 
time in which these are to be heated. 

This additional heat may be figured and allowed for as conditions re- 



TABLE 1. WINTER INSIDE DRY-BULB TEMPERATURES USUALLY SPECIFIED* 



TTFB 07 BUILDING 


DwjFAHR 


TYPH OP BUILDING 


DB&FAHE 


SCHOOLS 
Class rooms 


70-72 


THEATERS 
Seating space 


68-72 


Assembly rooms. .. 


68-72 


Lounge rooms. 


68-72 


Gymnasiums 


55-65 


Toilets 


68 


Toilets and baths 


70 






Wardrobe and locker rooms 
Kitchens.- . 


65-68 
66 


HOTELS 
Bedrooms and baths 


70 


Dining and lunch rooms. 


65-70 


Dining rooms 


70 


Playrooms. 


60-65 


Kitchens and laundries 


fifi 


Natatoriums. . 


75 


Ballrooms 


65-68 


HOSPITALS 
Private rooms. 


70-72 


Toilets and service rooms. 

FTOMES 


68 
70-72 


Private rooms (surgical) 


70-80 


STORES.-. _ 


65-68 


Operating rooms . , . 


70-95 


PUBLIC BUILDINGS 


68-72 


Wards 


68 


WARM AIR BATHS 


I2fi 


Kitchens and laundries. 


66 


STEAM BATHS 


110 


Toiler 


68 


FACTORIES AND MACHINE SHOPS 


fin ft*? 


Bathrooms-. 


70-80 


H OUNDRIES AND BOILER SHOPS 


Kfkftn 






PAINT SHOPS... 


80 











** ^S m08t T? >mf< i? able f < 5 r ' bulb temperature to be maintained depends on the relative humidity and 
Chapter 3 ^"^ " conaidered together constitute what is termed the effective temperature. 



134 



CHAPTER 7. HEATING LOAD 



quire, but inasmuch as the heating system proportioned for taking care 
of the heat losses will usually have, a capacity about 100 per cent greater 
than that required for average winter weather, and inasmuch as most 
buildings may either be continuously heated or have more time allowed 
for heating-up during the few minimum temperature days, no allowance 
is made except in the size of boilers or furnaces. 

INSIDE TEMPERATURES 

The inside air temperature which must be maintained within a building 
and which should always be stated in the heating specifications is under- 
stood to be the dry-bulb temperature at the breathing line, 5 ft above the 
floor, or the 30-in. line, and not less than 3 ft from the outside* walls. 
Inside air temperatures, usually specified, vary in accordance with the use 
to which the building is to be put and Table 1 presents values which con- 
form with good practice. 

The proper dry-bulb temperature to be maintained depends upon the 
relative humidity and air motion, as explained in Chapter 3. In other 
words, a person may feel warm or cool at the same dry-bulb temperature, 
depending on the relative humidity and air motion. The optimum winter 
effective temperature for sedentary persons, as determined at the A.S.H. 
V.E. Research Laboratory, is 66 deg. 1 

According to Fig. 6, Chapter 3, for so-called still air conditions, a 
relative humidity of approximately 50 per cent is required to produce an 
effective temperature of 66 deg when the dry-bulb temperature is 70 F. 
However, even where provision is made for artificial humidification, the 
relative humidity is seldom maintained higher than 40 per cent during the 
extremely cold weather, and where no provision is made for humidifica- 
tion, the relative humidity may be 20 per cent or less. Consequently, in 
using the figures listed in Table 1, consideration should be given to 
whether provision is to be made for humidification, and if so, the actual 
relative humidity to be maintained. 

Temperature at Proper Level: In making the actual heat-loss compu- 
tations, however, for the various rooms in a building it is often necessary 
to modify the temperatures given in Table 1 so that the air temperature 
at the proper level will be used. By air temperature at the proper level is 
meant, in the case of walls, the air temperature at the mean height be- 
tween floor and ceiling; in the case of glass, the air temperature at the 
mean height of the glass; in the case of roof or ceiling, the air temperature 
at the mean height of the roof or ceiling above the floor of the heated 
room ; and in the case of floors, the air temperature at the floor level. In 
the case of heated spaces adjacent to unheated spaces, it will usually be 
sufficient to assume the temperature in such spaces as the mean between 
the temperature of the inside heated spaces and the outside air tempera- 
ture, excepting where the combined heat transmission coefficient of the 
roof and ceiling can be used, in which case the usual inside and outside 
temperatures should be applied. (See discussion regarding the use of 
combined coefficients of pitched roofs, unheated attics and top-floor 
ceilings Chapter 5.) 



*See Chapter 3, p. 63. 

135 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

High Ceilings: Research data concerning stratification of air in build- 
ings are lacking, but in general it may be said that where the increase in 
temperature is due to the natural tendency of jthe warmer or less dense 
air to rise, as where a direct radiation system is installed, the temperature 
of the air at the ceiling increases with the ceiling height. The relation, 
however, is not a straight-line function, as the amount of increase per foot 
of height apparently decreases as the height of the ceiling increases, ac- 
cording to present available information 2 . 

Where ceiling heights are under 20 ft, it is common engineering practice 
to consider that the Fahrenheit temperature increases 2 per cent for each 
foot of height above the breathing line. This rule, sufficiently accurate 
for most cases, will give the probable air temperature at any given level 
for a room heated by direct radiation. Thus, the probable temperature 
in a room at a point 3 ft above the breathing line, if the breathing line 
temperature is 70 F, will be 

(1.00 + 3 X .02) 70 = 74.2 F. 

With certain types of heating and ventilating systems, which tend to 
oppose the natural tendency of warm air to rise, the temperature differ- 
ential between floor and ceiling can be greatly reduced. These include 
unit heaters, fan-furnace heaters, and the various types of mechanical 
ventilating systems. The amount of reduction is problematical in certain 
instances, as it depends upon many factors such as location of heaters, 
air temperature, and direction and velocity of air discharge. In some 
cases it has been possible to reduce the temperature between the floor 
and ceiling by a few degrees, whereas, in other cases, the temperature at 
the ceiling has actually been increased because of improper design, instal- 
lation or operation of equipment. So much depends upon the factors 
enumerated that it is not advisable to allow less than 1 per cent per foot 
(and usually more) above the breathing line in arriving at the air tem- 
perature at any given level for any of these types of heating and ventilating 
systems, unless the manufacturers are willing to guarantee that the par- 
ticular type of equipment under consideration will maintain a smaller 
temperature differential for the specific conditions involved. 

Temperature at Floor Level: In determining mean air temperatures 
just above floors which are next to ground or unheated spaces, a tempera- 
ture 5 deg lower than the breathing-line temperature may be used, pro- 
vided the breathing-line temperature is not less than 55 F. 

OUTSIDE TEMPERATURES 

The outside temperature used in computing the heat loss from a build- 
ing is seldom taken as the lowest temperature ever recorded in a given 
locality. Such temperatures are usually of short duration and are rarely 
repeated in successive years. It is therefore evident that a temperature 
somewhat higher than the lowest on record may be properly assumed in 
making the heat-loss computations. 



3 Temperature Gradient Observations in a Large Heated Space, by G. L. Larson, D. W. Nelson and 
O. C. Cromer (A.S.H.V.E. TRANSACTIONS, Vol. 39, 1933, p. 243). 

Tests of Three Heating Systems in an Industrial Type of Building, by G. L. Larson, D. W. Nelson and 
John James (A.S.H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 185). 

136 



CHAPTER 7. HEATING LOAD 



The outside temperature to be assumed in the design of any heating 
system is ordinarily not more than 15 deg above the lowest recorded tem- 
perature as reported by the Weather Bureau during the preceding 10 
years for the locality in which the heating system is to be installed. In 
the case of massive and^well insulated buildings in localities where the 
minimum does not prevail for more than a few hours, or where the lowest 
recorded temperature is extremely unusual, more than 15 deg above the 
minimum may be allowed, due primarily to the fly-wheel effect of the heat 
capacity of the structure. The outside temperature assumed and used in 
the design should always be stated in the heating specifications. Table 2 
lists the coldest dry-bulb temperatures ever recorded by the Weather 
Bureau at the places listed. 

If Weather Bureau reports are not available for the locality in question, 
then the reports for the station nearest to this locality are to be used, 
unless some other temperature is specifically stated in the specifications. 
In computing the average heat transmission losses for the heating season 
in the United States the average outside temperature from October 1 
to May 1 should be used. 

WIND VELOCITY EFFECTS 

The effect of wind on the heating requirements, of any building should 
be given consideration under two heads: 

1. Wind movement increases the heat transmission of walls, glass, and roof, affecting 
poor walls to a much greater extent than good walls. 

2. Wind movement materially increases the infiltration (inleakage) of cold air through 
the cracks around doors and windows, and even through the building materials them- 
selves, if such materials are at all porous. 

Theoretically as a basis for design, the most unfavorable combination 
of temperature and wind velocity should be chosen. It is entirely possible 
that a building might require more heat on a windy day with a moderately 
low outside temperature than on a quiet day with a much lower outside 
temperature. However, the combination of wind and temperature which 
is the worst would differ with different buildings, because wind velocity 
has a greater effect on buildings which have relatively high infiltration 
losses. It would be possible to work out the heating load for a^ building 
for several different combinations of temperature and wind velocity which 
records show to have occurred and to select the worst combination; but 
designers generally do not feel that such a degree of refinement is justified. 
Therefore, pending further studies of actual buildings, it is recommended 
that the average wind movement in any locality during December, 
January and February be provided for in computing (1) the heat trans- 
mission of a building, and (2) the heat required to take care of the infiltra- 
tion of outside air. 

The first condition is readily taken care of, as explained in Chapter 5, 
by using a surface coefficient / for the outside wall surface which is based 
on the proper wind velocity. In case specific data are lacking for any 
given locality, it is sufficiently accurate to use an average wind velocity of 
approximately 15 mph which is the velocity upon which the heat trans- 
mission coefficient tables in Chapter 5 are based. 

In a similar manner, the heat allowance for infiltration through cracks 

137 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 2. CLIMATIC CONDITIONS COMPILED FROM WEATHER BUREAU RECORDS** 



COL. A 


COL. B 


COL.C 


COL. D 


COL. E 


COL.F 


State 


City 


Average 
Temp., 
Oct. 1st- 
May 1st 


Lowest 
Tempera- 
ture 
Ever 
Reported 


Average 
Wind Vel- 
ocity Dec., 
Jan., Feb., 
Miles per 
Hour 


Direction 
of Prevail- 
ing Wind, 
Dec., Jan., 
Feb. 


Ala.. 


Mobile 


58.9 


-1 


10.4 


N 




Birmingham 


53.8 


-10 


8.5 


N 


Ariz 


Phoenix. 


59.5 


12 


6.4 


E 




Flagstaff. 


35.8 


-25 


7.8 


SW 


Ark __ 


Fort Smith 


50.4 


-15 


8.1 


E 




Little Rock 


51.6 


-12 


8.7 


NW 


Calif 


San Francisco 


54.2 


27 


7.6 


N 




Los Angeles 


58.5 


28 


6.3 


NE 


Colo 


Denver 


38.9 


-29 


7.5 


S 




Grand Junction 


38.9 


-21 


5.3 


NW 


Conn. 


New Haven 


38.4 


-15 


9.7 


N 


D. C. 


Washington 


43.4 


-15 


7.1 


NW 


Fla 


Jacksonville 


62.0 


10 


9.2 


NE 


Ga 


Atlanta 


51.5 


-8 


12.1 


NW 




Savannah 


58.5 


8 


9.5 


NW 


Idaho 


Lewiston 


42.3 


-23 


5.3 


E 




Pocatello 


35.7 


-28 


9.6 


SE 


111 


Chicago 


36.4 


-23 


12.5 


W 




Springfield 


39.8 


-24 


10.1 


NW 


Ind 


Indianapolis. 
Evansville 


40.3 
45.1 


-25 
-16 


11.5 
9.8 


SW 
S 


Iowa 


Dubuque... 


33.9 


-32 


7.1 


NW 




Sioux City 


32.6 


-35' 


11.6 


NW 


Kans 


Concordia 


39.8 


-25 


8.1 


S 


Ky. 


Dodge City 
Louisville 


41.4 
45.3 


-26 
-20 


9.8 
9.9 


NW 
SW 


La 


New Orleans 


61.6 


7 


8.8 


N 




Shreveport 


56.2 


-5 


8.9 


SE 


Me 


Eastport. 


31.5 


-23 


12.0 


W 




Portland 


33.8 


-21 


9.2 


NW 


Md 


Baltimore. 


43.8 


-7 


7.8 


NW 


Mass. 


Boston. 


38.1 


-18 


11.2 


W 


Mich 


Alpena 


29.6 


28 


12 4 


W 




Detroit 


35.8 


-24 


12.7 


SW 




Marquette 


28.3 


-27 


11.1 


NW 


Minn 


Duluth 


24 3 


41 


12.6 


SW 




Minneapolis. 


29.4 


-33 


n!s 


NW 


Miss 


Vicksburg. 


56.8 


-1 


8.3 


SE 


Mo 


St. Joseph 
St. Louis 


40.7 
43.6 


-24 
-22 


9.3> 
11.6 


NW 
S 


Mont 


Springfield 


44.3 
34.0 


-29 
-49 


10.8 


SE 
W 




Havre 


27.6 


-57 


~o 


SW 


Nebr 


Lincoln 


37.0 


-29 


10.5 


S 




North Platte 


35.4 


-35 


8.5 


W 


Nev .. 


Tonopah. 


39.4 


-10 


10.0 


SE 




Winnemucca 


37.9 


-28 


8.7 


NE 


N. H. .. 


Concord 


33.3 


-35 


6.6 


NW 


N. T. 

N.Y.:::::::::: 


Atlantic City 
Albany 


41.6 
35.2 


-9 
-24 


15.9 
8.1 


NW 
S 




Buffalo 


34.8 


-20 


17.2 


W 




New York 


40.7 


-14 


17.1 


NW 



^United States data from U. S. Weather Bureau. 
Canadian data from Meteorological Service of Canada. 

138 



CHAPTER 7. HEATING LOAD 



TABLE 2. CLIMATIC CONDITIONS COMPILED FROM WEATHER BUREAU RECORDS* 

(Continued) 



COL. A 


COL.B 


COL. C 


COL. D 


CouE 


CoL,F 


State 
or 
Province 


City 


Average 
Temp., 
Oct. 1st- 
May 1st 


Lowest 
Tempera- 
ture Ever 
Reported 


Average 
Wind Vel- 
ocity Dec., 
Jan., Feb., 
Miles per 
Hour 


Direction 
of Prevail- 
ing Wind, 
Dec., Jan., 
Feb. 


N. M 
N. C 

N. Dak 
Ohio 


Santa Fe. 
Raleigh.-. 
Wilmington 
Bismarck 
Devils Lake 
Cleveland 


38.3 
50.0 
54.2 
24.6 
20.3 
37 2 


-13 
-2 
5 
-45 
-44 
17 


7.8 
8.2 
8.5 
9.1 
10.6 
13 


NE 
SW 

sw 

NW 
W 

sw 


Okla 
Oreg 

Pa 

R I 


Columbus 
Oklahoma City 
Baker 
Portland 
Philadelphia 
Pittsburgh 
Providence. 


39.9 
47.9 
35.2 
46.1 
42.7 
41.0 
37.2 


-20 
-17 
-24 
-2 
-6 
-20 
-17 


12,0 
12.0 
6.9 
7.5 

11.0 
11.7 
12.8 


sw 

N 
SE 

S 

NW 
W 
NW 


s. c 


Charleston 


57.4 


7 


10.6 


SW 


S Dak. 


Columbia 
Huron 


54.0 
28.2 


-2 
-43 


8.1 
10.6 


NE 
NW 


Tenn 


Rapid City. 
Knoxville 
Memphis 


33.4 
47.9 
51.1 


-34 
-16 
-9 


8.2 
7.8 
9.7 


W 
SW 

s 


Texas 
Utah 


El Paso 
Fort Worth 
San Antonio 
Modena.. 

Salt Lake City 


53.5 
55.2 
60.6 
36.3 
40.0 


-5 
-8 
4 
-24 
-20 


10.4 
10.4 
8.0 
8.8 
6.7 


NW 
NW 
NE 
W 
SE 


Vt 
Va 

Wash 

W. Va. 


Burlington 
Norfolk. 
Lynchburg. 
Richmond 
Seattle 
Spokane 
Elkins 


31.5 
49.3 
46.8 
47.0 
44.8 
37.7 
39.4 


-29 
2 
-7 
-3 
3 
-30 
-28 


11.8 
12.5 
7.1 
7.9 
11.3 
7.1 
6.6 


S 
N 
NW 
SW 
SE 
SW 
W 


Wis 


Parkersburg. 
Green Bay 


42.6 
30.0 


-27 
-36 


7.5 
10.4 


SW 

SW 


Wyo. 

Alta. 
B. C 


La Crosse~ 
Milwaukee.. 

Lander 
Edmonton 

Victoria 


31.7 
33.4 
30.7 
30.0 
23.0 
43.9 


-43 
-25 
-41 
-40 
-57 
- 1.5 


7.3 
11.5 
6.0 
5.0 
6.5 
12.5 


s 

W 

NW 
SW 

sw 

N 


Man 

N B 


Vancouver 
Winnipeg 

Fredericton 


42.0 
17.5 
27.0 


2 

-47 
35 


4.5 
10.0 
9.6 


E 

NW 
NW 


N. S 
Ont. 


Yarmouth 

London 


35.0 
32.6 


-12 
-27 


14.2 
10.3 


NW 
SW 




Ottawa 
Port Arthur 

Toronto 


26.5 
22.4 
32.9 


-34 
-37 
-26.5 


8.4 
7.8 
13.0 


NW 
NW 
SW 


P. E. I 
Que 


Charlottetown 
Montreal 


29.0 

27.8 


-27 
-29 


9.4 
14.3 


sw 
sw 


Sask.._ 
Yukon 


Quebec 
Prince Albert 
Dawson 


24.2 
15.8 
2.1 


-34 
-70 
-68 


13.6 
5.1 
3.7 


sw 

W 

s 



^United States data from U. S. Weather Bureau. 
Canadian data from Meteorological Service of Canada. 

139 



HEATING VENTIUITING AIR CONDITIONING GUIDE 1938 

and walls (Tables 1 and 2, Chapter 6) must be based on the proper wind 
velocity for a given locality. In the case of tall buildings special attention 
must be given to infiltration factors. (See Chapter 6). 

In the past many designers have used empirical exposure factors which 
were arbitrarily chosen to increase the calculated heat loss on the side or 
sides of the building exposed to the prevailing winds. It is also possible 
to differentiate among the various exposures more accurately by calcu- 
lating the infiltration and transmission losses separately for the different 
sides of the building, using different assumed wind velocities. Recent 
investigations show, however, that the wind direction indicated by 
Weather Bureau instruments does not always correspond with the 
direction of actual impact on the building walls, due to deflection by 
surrounding buildings. 

The exposure factor, which is still in use by many engineers, is usually 
taken as 15 per cent, and is added to the calculated heat loss on the side or 
sides exposed to what is considered the prevailing winter wind. There is a 
need for actual test data on this point, and pending the time when it can 
be secured, the question must be left to the judgment of the designing 
engineer. It should be remembered that the values of U in the tables in 
Chapter 5 are based on a wind velocity of 15 mph and that the infiltration 
figures are supposed to be selected from the tables in Chapter 6 to cor- 
respond to the wind velocities given in Table 2 of the present chapter. 

The Heating, Piping and Air Conditioning Contractors National Associ- 
ation has devised a method 8 for calculating the square feet of equivalent 
direct radiation required in a building. This method makes use of ex- 
posure factors which vary according to the geographical location and the 
angular situation of the construction in question in reference to pre- 
vailing winds and the velocity of them. 

AUXILIARY HEAT SOURCES 

The heat supplied by persons, lights, motors and machinery should 
always be ascertained in the case of theaters, assembly halls, and in- 
dustrial plants, but allowances for such heat sources must be made only 
after careful consideration of all local conditions. In many cases, these 
heat sources should not be allowed to affect the size of the installation at 
all, although they may have a marked effect on the operation and con- 
trol of the system. In general, it is safe to say that where audiences are 
involved, the heating installation must have sufficient capacity to bring 
the building up to the stipulated inside temperature before the audience 
arrives. In industrial plants, quite a different condition exists, and heat 
sources, if they are always available during the period of human occu- 
pancy, may be substituted for a portion of the heating installation. In 
no case should the actual heating installation (exclusive of heat sources) 
be reduced below that required to maintain at least 40 F in the building. 

Electric Motors and Machinery 

Motors and the machinery which they drive, if both are located in the 
room, convert all of the electrical energy supplied into heat, which is 



See Standards of Heating, Piping and Air Conditioning Contractors National Association. 

140 



CHAPTER 7. HEATING LOAD 



retained in the room if the product being manufactured is not removed 
until its temperature is the same as the room temperature. 

If power is transmitted to the machinery from the outside, then only 
the heat equivalent of the brake horsepower supplied is used. In the 

first case the Btu supplied per hour = Motor horsepower and 

Efficiency of motor 

in the second case Btu per hour = bhp X 2546, in which 2546 is the 
Btu equivalent of 1 hp-hour. In high-powered mills this is the chief 
source of heating and it is frequently sufficient to overheat the building 
even in zero weather, thus requiring cooling by ventilation the year 
round. 

The heat (in Btu per hour) from electric lamps is obtained by multi- 
plying the watts per lamp by the number of lamps and by 3.415. One 
cubic foot of producer gas gives off about 150 Btu per hour; one cubic 
foot of illuminating gas gives off about 535 Btu per hour; and one cubic 
foot of natural gas gives off about 1000 Btu per hour. A Welsbach 
burner averages 3 cu ft of gas per hour and a fish-tail burner, 5 cu ft 
per hour. For information concerning the heat supplied by persons, 
see Chapter 3. 

In intermittently heated buildings, besides the capacity necessary 
to care for the normal heat loss which may be calculated according to 
customary rules, additional capacity should be provided to supply the 
heat necessary to warm up the cold material of the interior walls, floors, 
and furnishings. Tests have shown that when a cold building has had its 
temperature raised to about 60 F from an initial condition of about F, 
the heat absorbed from the air by the material in the structure may vary 
from 50 per cent to 150 per cent of the normal heat loss of the building. 
It is therefore necessary, in order to heat up a cold building within a 
reasonable length of time, to provide such additional capacity. If the 
interior material is cold when people enter a building, the radiation of 
heat from the occupants to the cold material will be greater than is 
normal and discomfort will result. (See Chapter 3.) 

WALL CONDENSATION 

Condensation in the interior surfaces 4 of buildings may cause irrep- 
arable damage to manufactured articles and machinery. It often results 
in short-circuiting of electric power, and causes disintegration of roof 
structures not properly protected. 

The prevalence of moisture on a surface is caused by the contact of 
the warm humid air in a building with surfaces below the dew-point 
temperature. It can be eliminated by (1) raising the surface temperature 
with increased air velocities passing over the surface, or adding a sufficient 
thickness of insulation, and (2) by lowering the humidity which is often 
not possible due to manufacturing processes. 

The condensation of moisture within walls 5 is an important problem 
with may types of construction under adverse conditions. The tempera- 

*Preventing Condensation on Interior Building Surfaces, by Paul D. Close (A.S.H.V.E. TRANSACTIONS, 
Vol. 36, 1930, p. 153). 

"Condensation within Walls, by F. B. Rowley, A. B. Algren and C. E. Lund (A.S.H.V.E. JOURNAL 
SECTION, Healing, Piping and Air Conditioning, January, 1938). 

141 



HEATING VENTIIATING AIR CONDITIONING GUIDE 1938 

tures of the various parts of a wall are controlled by the type and amount 
of insulation used and the vapor densities in the corresponding sections 
are controlled by the type of vapor barriers installed. The transmission 
of heat and vapor through a wall should be considered together, and in 
most cases the proper combination of insulation and vapor barriers will 
eliminate the possibilities of condensation within walls. A consideration 
often overlooked in problems of condensation within walls is that a vapor 
barrier should be placed on the warm side and not on the cold side of 
a wall. 

HEAT LOSS COMPUTATION EXAMPLE 



Buift-up Cooftoq on 3* CoocrVe Hoof Deck 



5fe U UnqAwfcnol Ax* MorHi * S 

#e 1 

net 1 IS Window* od 
l.f r de 4'JfUuLt. 
fcron 1 
nor i* 5*St&neConcrae0n 
faec-fn-p 3-OndrCooct 
j' OR Dirt -7 


outh 


Lenqlb ttrf-0* 

\ 




S 


O 

I 

r 


orCra 
Solid V 


&~ 

xxlDoow 

-BP 




5 









FIG. 1. ELEVATION OF FACTORY BUILDING 



Philadelphia, Pa. 

-6F 



..Northwest 
60 F 



1. LOCATION 

2. LOWEST OUTSIDE TEMPERATURE. (Table 2) 

3. BASE TEMPERATURE: In this example a design temperature 10 F above lowest 

on record instead of 15 F is used. Hence the base temperature 

(- 6 + 10) = + 4 F. 

4. DIRECTION OF PREVAILING WIND (during Dec., Jan., Feb.) 

5. BREATHING-LINE TEMPERATURE (5 ft from floor) 

6. INSIDE AIR TEMPERATURE AT ROOF: 

The air temperature just below roof is higher than at the breathing line. 
Height of roof is 16 ft, or it is 16 5 11 ft above breathing line. Allowing 
2 per cent per foot above 5 ft, or 2 X 11 22 per cent, makes the tem- 
perature of the air under the roof = 1,22 X 60 = 73.2 F. 

7. INSIDE TEMPERATURE AT WALLS: 

The air temperature at the mean height of the walls is greater than at 
the breathing fine. The mean height of the walls is 8 ft and allowing 2 per 
cent per foot above 5 ft, the average mean temperature of the walls is 
1.06 X 60 = 63.6 F. By similar assumptions and calculations, the mean 
temperature of the glass will be found to be 64.2 F and that of the doors 
61.2 F. 



8. AVERAGE WIND VELOCITY (Table 2) 

9. OVER-ALL DIMENSIONS (See Fig. 1)... 
10. CONSTRUCTION: 



..11.0 mph 



120 x 50 x 16 ft 



Walls 12-in. brick, with %-in. plaster applied directly to inside surface. 
Roof 3-in. stone concrete and built-up roofing. 

142 



CHAPTER 7. HEATING LOAD 



Floor 5-in. stone concrete on 3-in. cinder concrete on dirt. 

Doors One 12 ft x 12 ft wood door (2 in. thick) at each end. 

Windows Fifteen, 9 ft x 4 ft single glass double-hung windows on each side. 

11. TRANSMISSION COEFFICIENTS: 

Walls (Table 3, Chapter 5, Wall 2B) U = 0.34 

Roof (Table 11, Chapter 5, Roofs 2A and 3A) U = 0.77 

Floor (Table 10, Chapter 5, Floors 5A and 6A) U = 0.63 

Doors -(Table 13B, Chapter 5) U = 0.46 

Windows (Table 13A, Chapters) U - 1.13 

12. INFILTRATION COEFFICIENTS: 

Windows Average windows, non-weatherstripped, Ke-i n - crack and 
5^4-in. clearance. The leakage per foot of crack for an 11-mile wind 
velocity is 25.0 cfh. (Determined by interpolation of Table 2, 
Chapter 6.) The heat equivalent per hour per degree per foot of 
crack is taken from Chapter 6. 

25.0 X 0.018 = 0.45 Btu per deg Fahrenheit per foot of crack. 

Doors Assume infiltration loss through door crack twice that of windows 
or 2 X 0.45 = 0.90 Btu per deg Fahrenheit per foot of crack. 

Walls As shown by Table 1, Chapter 6, a plastered wall allows so little 
infiltration that in this problem it may be neglected. 

13. CALCULATIONS: See calculation sheet, Table 3. 



TABLE 3. 



CALCULATION SHEET SHOWING METHOD OF ESTIMATING HEAT LOSSES OF 
BUILDING SHOWN IN FIG. 1 



PART OF BUILDING 


WIDTH 

IN 

FEET 


HEIGHT 

IN 

FEET 


NET SUR- 
FACE AREA 
OR CRACK 
LENGTH 


COEFFI- 

CIENT 


TEMP. 
DIFF. 


TOTAL 
BTU 


North Wall: 
Pn>k, M- 1 "^ piaster , ., 


60 
12 

Ipair 


16 
12 
doors 


656 
144 
60 


0.34 
0.46 
0.90 


59.6 
57.2 
57.2 


13,293 
3,789 
1,544* 


Poors (2-ii?T wood) , 


Min- ^rac.k -. ' 


West Wall: 

Ttriclc, J^-in . pfastfr 


120 
15x4 
Double 
Windov 


16 
9 
Hung 
re (15) 


1380 
540 

450 


0.34 
1.13 

0.45 


59.6 
60.2 

60.2 


27,964 
36,734 

6,095a 


niass (Siiigte) L _ 


^ in Cr?cV .... ~ , - 




South Wall 


Same as North Wall 




18,626 


TCaat Ws^l , 


Same as West Wall 




70,793 




Roof, 3-in. concrete and slag- 
surfaced built-up roofing 


50 


120 


6000 


0.77 


69.2 


319,704 


Floor, 5-in. stone concrete on 
3-in. cinder concrete.^_..____ 


50 


120 


6000 


0.63 


5b 


18,900 


GRAND TOTAL of heat required for building in Btu pet 


honr ,-,- L _^ 1L 


517.442 





aThis building has no partitions and whatever air enters through the cracks on the windward side must 
leave through the cracks on the leeward side. Therefore, only one-half of the total crack will be used in 
computing infiltration for each side and each end of building. 

bA 5 F temperature differential is commonly assumed to exist between the air on one side of a large 
floor laid on the ground and the ground. 



143 



HEATING VENTILATING Am CONDITIONING GUIDE 1938 



PROBLEMS IN PRACTICE 

1 What is the relation between the sensible heat loss from a building and the 
heat required for humidification? 

A house with a volume of 14,000 cu ft has a heat loss 120 Mbh for standard uninsulated 
frame construction and a 70 F temperature difference. Assuming a leakage rate of 
1J^ air changes per hour it would require about 10 Mbh to maintain a relative humidity 
of 45 per cent when the outside air is F and 50 per cent relative humidity. By using 
an insulation such as rock wool, the sensible heat loss of this house may be reduced to 
approximately 77 Mbh. The insulation does not affect the humidification load, which 
now assumes greater importance. 

2 What inside dry-bulb temperatures are usually assumed for: (a) homes, 
(b) schools, (c) public buildings? 

Referring to Table 1: 

a. 70 to 72 F. 

b. Temperature varies from 55 to 75 F, depending on the room. Classrooms, for instance, 
are usually specified as 70 to 72 F. 

c. 68 to 72 F. 

3 How is the outside temperature selected for use hi computing heat losses? 

The outside temperature used in computing heat losses is generally taken from 10 to 15 F 
higher than the lowest recorded temperature as reported by the Weather Bureau during 
the preceding 10 years for the locality in which the heating system is to be installed. 
In some cases where the lowest recorded temperature is extremely unusual, the design 
temperature is taken even higher than 15 F above the lowest recorded temperature. 

4 What are the effects of wind movement on the heating load? 

a. Wind movement increases the heat transmission of walls, glass, and roof; it affects 
poor walls to a much greater extent than good walls. 

b. Wind movement materially increases the infiltration (inleakage) of cold air through 
the cracks around doors and windows, and even through the building materials them- 
selves if such materials are at all porous. 

5 Calculate the heat given off by eighteen 200-watt lamps. 

200 X 18 X 3.415 - 12,294 Btu per hour. 

6 A two-story, six-room, frame house, 28-ft by 30-ft foundation, has the 
following proportions : 

Area of outside walls, 1992 sq ft. 

Area of glass, 333 sq ft. 

Area of outside doors, 54 sq ft. 

Cracks around windows, 440 ft. 

Cracks around doors, 54 ft. 

Area of second floor ceiling, 783 sq ft. 

Volume, first and second floors, 13,010 cu ft. 

Ceilings, 9 ft high. 

The minimum temperature for the heating season is 34 F, and the required 
inside temperature at the 30-in. level is 70 F. The average number of degree 
days for a heating season is 7851, and the average wind velocity is 10 mph, 
northwest. * 



The walls are constructed of 2-m. by 4-in. studs with wood sheathing, building 
paper, and wood siding on the outside, and wood lath and plaster on the inside. 
Windows are single glass, double-hung, wood, without weatherstrips. The 
second floor ceiling is metal lath and plaster, without an attic floor. The roof 
is of wood shingles on wood strips with rafters exposed. The area of the roof is 
20 per cent greater than the area of the ceiling. Select values for the following : 
(a) U for walls; (b) U for glass; (c) U for second floor ceiling; (d) U for roof; 



144 



CHAPTER 7. HEATING LOAD 



(e) U for ceiling and roof combined; (f) air leakage, cubic feet per hour per foot 
of window crack; (g) air leakage, cubic feet per hour per foot of door crack. 

a. 0.25 (Table 5, Chapter 5). 

b. 1.13 (Table 13, Chapter 5). 

c. 0.69 (Table 8, Chapter 5). 

d. 0.46 (Table 12, Chapter 5). 

e. 0.31 (Equation 6, Chapter 5). 
/. 21.4 (Table 2, Chapter 6). 

g. 42.8, which is double the window leakage. 

7 Using the data of Question 6, calculate the maximum Btu loss per hour for 
the various constructions, and show the percentage of the total heat which is 
lost through each construction described. 

Assume 2 per cent rise in temperature for each foot in height. The average temperature 
will be 72.8 F for walls, doors, and windows, and 79.1 F for the second floor ceiling. 



a. Outside walls 

b. Glass 

c. Doors 

d. Second floor ceiling 

e. Air leakage, windows 
/. Air leakage, doors 

Total 



46,200 Btu loss 
34,950 Btu loss 

5,670 Btu loss 
24,050 Btu loss 
15,750 Btu loss 

3,865 Btu loss 



35.4 per cent of total 
26.7 per cent of total 

4.4 per cent of total 
18.4 per cent of total 
12.1 per cent of total 

3.0 per cent of total 



130,485 Btu loss 100.0 per cent of total 

8 For the house in Question 6, place 1-in. insulation in the outside walls and 
second floor ceiling; k for insulation = 0.34. Use weatherstrip on doors and 
windows, and double glass on the windows; G = 0.55. Calculate or select the 
following values: (a) U for walls; (b) U for glass; (c) U for second floor ceiling; 
(d) U for combination of ceiling and roof; (e) air leakage, cubic feet per hour 
per foot of door crack; (f) air leakage, cubic feet per hour per foot of window 
crack. 

a. 0.144 

b. 0.55 

c. 0.23 

d. 0.16 

e. 15.5 
/. 31.0 

9 Calculate the maximum Btu loss per hour and show the percentage loss by 
each channel for the house as insulated in Question 8. 



a. Outside walls 

b. Glass 

c. Doors 

d. Ceiling 

e. Air leakage, windows 
/. Air leakage, doors 

Total 



26,650 Btu loss 
17,000 Btu loss 

5,670 Btu loss 
12,420 Btu loss 
11,400 Btu loss 

2,795 Btu loss 



35.1 per cent of total 
22.4 per cent of total 

7.4 per cent of total 
16.4 per cent of total 
15.1 per cent of total 

3.6 per cent of total 



75,935 Btu loss 100.0 per cent of total 



10 From the results of Questions 7 and 9, calculate the Btu saved and the 
percentage saved by each change in construction. 





UNINSULATED 


INB^ 


BTU SAVED 


Fra CENT SATED 


a. Outside walls 
b. Glass 
c. Doors 
d. Ceiling 


46,200 
34,950 
5,670 
24,050 
15,750 
3,865 


26,650 
17,000 
5,670 
12,420 
11,400 
2,795 


19,550 
17,950 

11,630 
4,350 
1,070 


42.3 
51.4 

48.3 
27.6 
27.7 


f. Air leakage, windows 


/. Air leakage, doors. 



145 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

11 From the results of Questions 7 and 9, calculate the heat loads per heating 
season in Btu and note the savings by better construction. 

The 7851 degree days for the heating season multiplied by 24 hours, times the Btu loss 
per hour for 1 F drop in temperature gives the Btu load per heating season. 

Saving - 262,000,000 - 152,500,000 = 109,500,000 Btu. 

12 The dry-bulb temperature and the relative humidity at the ceiling of a 
mixing room in a bakery are 80 F and 60 per cent, respectively. The roof is a 
4-in. concrete deck covered with built-up roofing. If the lowest outside tem- 
perature to be expected is 10 F, what thickness of rigid fiber insulation will be 
required to prevent condensation? 

From Table 11, Chapter 5, U for the uninsulated roof = 0.72. From Table 2, Chapter 5, 
k for rigid fiber insulation = 0.33. From the psychrometric chart the dew-point of air 
at 80 F and 60 per cent relative humidity is 65 F. The ceiling temperature, therefore, 
must not drop below 65 F if condensation is to be prevented. 

When equilibrium is established, the amount of heat flowing through any component 
part of a construction is the same for each square foot of area. 

Therefore, 

U [80 - (-10) ] = 1.65 (80 - 65) 
where 

U is the transmittance of the insulated roof. 
Solving the equation, U = 0.275. 

The resistance of the insulated roof = ~ _, = 3.64. 



The resistance of the uninsulated roof = 77-^7 1.39. 

U.7J 

The resistance of the insulation = 3.64 1.39 = 2.25. 

Resistance per inch of insulation = n Q0 = 3.0. 

U.oo 

Since a resistance of 2.25 is required, and 1 in. of insulation has a resistance of 3, one inch 
will be sufficient to prevent condensation. 

The same result might have been obtained by selecting an insulated 4-in. concrete slab 
having a U of less than 0.275 from Table 11, Chapter 5. This 4-in. concrete slab with 
1-in. rigid insulation has a U of 0.23 which is safe. 



146 



L 



Chapter 8 

COOLING LOAD 

Conditions of Comfort, Design Outside Temperatures, Com- 
ponents of Heat Gain, Normal Heat Transmission, Solar 
Heat Transmission, Sun Effect Through Windows, Heat 
Emission of Occupants, Heat Introduced by Outside Air, Heat 
Emission of Appliances 

OAD calculations for summer air conditioning are more complicated 
, y than heating load calculations for the reason that there are several 
more factors to be considered. Because of the variable nature of some of 
the contributing load components and the fact that they do not neces- 
sarily impose their maximum effect simultaneously, considerable care 
must be exercised in determining their phase relationship in order that 
equipment of proper capacity may be selected to maintain specified 
indoor conditions. 

CONDITIONS OF COMFORT 

The conditions to be maintained in an enclosure are variable ^ and 
depend upon several factors, especially the outside design conditions, 
duration of occupancy and relationship between air motion, dry-bulb and 
wet-bulb temperatures. Information concerning the proper effective 
temperature to be maintained is given in Chapter 3, where are also tabu- 
lated the most desirable indoor conditions to be maintained in summer for 
exposures over 40 min (see Table 2, Chapter 3). 

DESIGN OUTSIDE TEMPERATURES 

Summer dry-bulb and wet-bulb temperatures of various cities are 
given in Table 1. It will be noted that the temperatures are not the maxi- 
mums but the design temperatures which should be used In air condition- 
ing calculations. The maximum outside wet-bulb temperatures as given 
in Weather Bureau reports usually occur only from 1 to 4 per cent of the 
time, and they are therefore of such short duration that it is not practical 
to design a cooling system covering this range. The temperatures shown 
in Table 1 are in part based on available design conditions known ^to be 
successfully applied and for those localities where this information is 
lacking they are based on a study of the hourly temperatures in New York 
City from which factors were derived and applied to the average maxi- 
mum dry- and wet-bulb temperatures for other cities. This study covered 
a twenty-year record of Weather Bureau temperatures. The design 

147 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 1. DESIGN DRY- AND WET-BULB TEMPERATURES, WIND VELOCITIES, AND 
WIND DIRECTIONS FOR JUNE, JULY, AUGUST, AND SEPTEMBER 



STATE 


CITY 


DESIGN 
DST-BULB 


DESIGN 
WET-BULB 


SUMMER WIND 
VELOCITY 
MPH 


PREVAILING 
SUMMER WIND 
DIRECTION 


Ala 


Birmingham 

Mobile 


95 
95 


78 
80 


5.2 

8.6 


S 

sw 


Ariz 


Phoenix 


105 


76 


6.0 


w 


Ark. . . 


Little Rock 


95 


78 


7.0 


NE 


Calif. 


Los Angeles 


90 


70 


6.0 


SW 


Colo. 


San Francisco 
Denver 


90 
95 


65 
64 


11.0 
6.8 


sw 

S 


Conn 


New Haven 


95 


75 


7.3 


S 


Dela. 
D. C. 


Wilmington 

Washington 


95 
95 


78 
78 


9.7 
6.2 


sw 

S 


Fla. 


Jacksonville, 


95 


78 


8.7 


sw 




Tampa 


94 


79 


7.0 


E 


Ga 


Atlanta 


95 


75 


7.3 


NW 


Idaho . ... 


Savannah 
Boise., _.... 


95 
95 


78 
65 


7.8 
5.8 


SW 

NW 


Ill 

Ind _. 
Iowa 
Kansas 
Ky. 

La v : :: 

Maine. 
Md 
Mass. 
Mich 
Minn ~ 
Miss. 
Mo 

Mont_ 


Chicago _ 
Peoria 
Indianapolis 
Des Moines 
Wichita 
Louisville 
New Orleans 
Portland- 
Baltimore.- 
Boston 
Detroit 
Minneapolis.- 
Vicksburg 
Kansas City. 
St. Louis. 
Helena 


95 
95 
95 
95 
100 
95 
95 
90 
95 
92 
95 
95 
95 
100 
95 
95 


75 

76 
76 
77 
75 
76 
79 
73 
78 
75 
75 
75 
78 
76 
78 
67 


10.2 
8.2 
9.0 
6.6 
11.0 
8.0 
7.0 
7.3 
6.9 
9.2 
10.3 
8.4 
6.2 
9.5 
9.4 
7.3 


NE 
S 
SW 

sw 

S 

sw 
sw 

S 

sw 
sw 
sw 

SE 

sw 

S 

sw 
sw 


Nebr 
Nev . 

N. H. 
N. J. 

N. Y. 


Lincoln 
Reno 
Manchester 
Trenton 

Albany 


95 
95 
90 
95 
92 


75 
65 
73 
78 
75 


9.3 

7.4 
5.6 
10.0 

71 


S 

w 

NW 

sw 
s 




Buffalo 
New York 


93 
95 


75 
75 


12.2 
12.9 


sw. 
sw 


N. M.. 


Santa Fe 


90 


65 


6 5 


SE 


N. C. 


Asheville. 


90 


75 


5.6 


SE 


N. Dak _ 
Ohio 

Okla 
Ores.. 

psZ :. ... 


Wilmington 
Bismarck 
Cleveland 
Cincinnati 
Oklahoma City 
Portland 
Philadelphia- 


95 
95 
95 
95 
101 
90 
95 


79 
73 

75 
78 
76 
65 
78 


7.8 
8.8 
9.9 
6.6 
10.1 
6.6 
97 


SW 

NW 
S 

sw 

s 

NW 
SW 


R. I 
S. C 

S. Dak 
Tenn. 


Pittsburgh 
Providence. 
Charleston 
Greenville. 
Sioux Falls 
Chattanooga 


95 
93 
95 
95 
95 
95 


75 
75 
80 
76 
75 
77 


9.0 
10.0 
9.9 
6.8 
7.6 
6 5 


NW 
NW 
SW 
NE 
S 
SW 




Memphis 


95 


78 


7.5 


sw 



148 



CHAPTER 8. COOLING LOAD 



TABLE 1. DESIGN DRY AND WET-BULB TEMPERATURES, WIND VELOCITIES, AND 
WIND DIRECTIONS FOR JUNE, JULY, AUGUST, AND SEPTEMBER (Continued) 



STATE 



Crrr 



DESIGN 
DET-BCLB 



SUMMER WIND i PBIVAUJNG 
VELOCITY i SUMMER WIND 











Mm 


JLHRECriON 


Texas 


Dallas 


100 


78 


9.4 


s 




Galveston.. _ 


95 


SO 


9.7 


s 




San Antonio 


100 


78 


7.4 


SE 




Houston 


95 


78 


7.7 


S 




El Paso,... 


100 


69 


6.9 


E 


Utah 


Salt Lake City 


95 


67 


8.2 


SE 


Vt 


Burlington 


90 


73 


8.9 


S 


Va 


Norfolk...... 


95 


78 


10.9 


S 




Richmond 


95 


78 


6.2 


SW 


Wash. 


Seattle. 


85 


65 


7.9 


S 




Spokane .... 


90 


65 


6.5 


SW 


W. Va 


Parkersburg 


95 


75 


5.3 


SE 


Wise. 


Madison. 


95 


75 


8.1 


SW 




Milwaukee. 


95 


75 


10.4 


s 


Wyo. _ 


Cheyenne. 


95 


65 


9.2 


s 















temperatures given are not exceeded more than 5 to 8 per cent of the time 
during a cooling season of 1200 hours in June, July, August and September 
for an average year. 

COMPONENTS OF HEAT GAIN 

A cooling load determination is composed of five components which 
may be classified in the following manner: 

1. Normal heat transfer through windows, walls, partitions, doors, floors, ceilings, etc. 

2. Transfer of solar radiation through windows, walls, doors, skylights, or roof. 

3. Heat emission of occupants within enclosures. 

4. Heat introduced by infiltration of outside air or controlled ventilation. 

5. Heat emission of mechanical, chemical, gas, steam, hot water and electrical 
appliances^located within enclosures. 

The components of heat gain, classified by source are further classified 
as sensible and latent heat gain. 

The first two components fall into the classification of sensible heat 
gain, that is, they tend to raise the temperature of the air within the 
structure. The last three components not only produce sensible heat 
gain but they may also tend to increase the moisture content of the air 
within the structure. 

Normal Heat Transmission 

By normal heat transmission, as distinguished from solar heat trans- 
mission is meant the transmission of heat through windows, walls, 
partitions, etc. from without to interior of enclosure by virtue of difference 
between outside and inside air temperatures. This load is calculated in a 

149 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 




8 



I 



CO 



8 



nia 



CHAPTER 8. COOLING LOAD 



manner similar to that described in Chapter 7 (except that flow of heat 
is reversed) by means of the formula: 

H t = AU(h-t) (1) 

where 

Ht = heat transmitted through the material of wall, glass, floor, etc., Btu per hour. 
A net inside area of wall, glass, floor, etc., square feet. 
t = inside temperature, degrees Fahrenheit. 
t = outside temperature, degrees Fahrenheit. 

U = coefficient of transmission of wall, glass, floor, etc., Btu per hour per square foot 
per degree Fahrenheit difference in temperature (Tables 3 to 13, Chapter 5), 

Solar Heat Transmission 

Calculations of the solar heatjtransmitted through walls and roofs 
are difficult to determine because of periodical character of heat flow and 
time lag due to heat capacity of construction. 

The variation in solar intensity normal to sun in Btu per square foot 
per hour on a horizontal surface, and on east, west, and south walls is 
given in Fig. 1. The curves are drawn from A.S.H.V.E. Laboratory data 
obtained by pyrheliometer, are based on sun time and apply for a per- 
fectly clear day on August 1 at a north latitude of 40 deg. A study of 
these curves discloses the periodic relationship and wide variation in 
solar intensity on various surfaces. It will be observed that both the roof 
and south wall radiation curves are in exact phase relationship with each 
other and that whereas the east and west wall radiation curves overlap 
those for roof and south wall, they do not overlap each other. This phase 
relationship has an important bearing on the cooling load. Failure to 
consider the periodical character of heat flow resulting from diurnal 
movement of the sun and the lag due to heat capacity of the structure, 
which determine the timing and magnitude of the heat wave flowing 
through the wall, may result in a large error in load calculations. 

The values of solar intensity appearing in Fig. 1 must not be confused 
with the actual heat transmission through the wall for much of this heat 
intensity on an outside surface is in part reflected and in part wiped off by 
convection to the outside air. A mathematical solution for the deter- 
mination of solar heat transmission has been developed but the equations 
involved are too complex for practical application. 1 From results of this 
investigation and earlier studies, 2 the Research Laboratory has prepared 
Tables 2, 3, 4 and 5 which give the solar intensity (I) for various hours of 
the day against walls of various orientations and horizontal surfaces and 
the solar radiation ( JG ) transmitted through windows of various orien- 
tations as well as skylights at various hours of the day. These values are 
shown for north latitudes from 30 to 45 deg. 

It should be noted that the values for (7) represent the rate of solar 
intensity impinging against and not transmitted through walls and roofs 
whereas values for (7 G ) represent actual rate of heat transmission through 
windows and skylights. Since the amount of solar intensity actually 

1 Heat Transmission as Influenced by Heat Capacity and Solar Radiation, by F. C. Houghten, J. L. 
Blackshaw, E. W. Pugh and Paul McDennott (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 231). 

Absorption of Solar Radiation in its Relation to the Temperature, Color, Angle and Other Character- 
istics of the Absorbing Surface, by F. C. Houghten and Carl Gutberlet (A.S.H.V.E. TRANSACTIONS, Vol. 
36, 1930, p. 137). - . _ . . . 

151 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 2. SOLAR RADIATION IMPINGING AGAINST WALLS HAVING SEVERAL ORIENTATIONS, 

AND A HORIZONTAL SURFACE, AND THE RADIATION TRANSMITTED THROUGH GLASS 

FOR THE SAME ORIENTATIONS 

For 30 Deg Latitude on the twenty-first of July, in Btu per sqft per hour 



SUN 


NORTHEAST EAST SOUTHEAST SOUTH SOUTHWEST i WIST 


NORTHWEST 


HORIZONTAL 
SURFACE 


TnoB 
















I 


I G , I 


IG I 


I G I ' 1 G I I I G 
















4:59 











; ' 


! 








5:00; 1 


0.9 1 


0.9 0.3 


02 ' , 






0.01 


0.005 


6:00 47 


41 51 


44 , 24 


17 : 






9 


5 


7:00 


136 


106 160 


140 , 90 


68 ' ; 




68 


47 


8:00 


151 


122 205 


177 136 


105 












147 


116 


9:00 


127 


91 189 


156 , 140 


104 


8 1 












214 


182 


10:00! 79 


47 , 141 


103 122 


85 


31 12 




j 






265 


231 


11:00 21 


6 ' 78 


45 85 


52 


45 21 














296 


261 


12:00 






36 


15 50 24 


36 


15 










305 


269 


1:00 










45 21 


85 


52 


78 


45 


21 


6 


296 


261 


2:00 




31 12 


122 


85 


141 


103 


79 


47 


265 


231 


3:001 ', 




8 1 


140 


104 


189 


156 


127 


91 


214 


182 


4:00 












136 


105 


205 


177 


151 


122 


147 


116 


5:00 












90 


68 


160 


140 


136 


106 


68 


47 


6:00j 








24 


17 


51 


44 


47 


41 


9 


5 


7:00; 




0.3 


0.2 


1 


0.9 


1 


0.9 


0.01 


0.005 


7:01 




; 


1 




j o 
























TABLE 3. SOLAR RADIATION IMPINGING AGAINST WALLS HAVING SEVERAL ORIENTATIONS, 

AND A HORIZONTAL SURFACE, AND THE RADIATION TRANSMITTED THROUGH GLASS 

FOR THE SAME ORIENTATIONS 

For 85 Deg Latitude on the twenty-first of July, in Btu per sqft per hour. 



i 
STO Nosn 

TtMB! 


HAST 


& 


5T 


Soum 


3EAST 


Soi 


JTH 


SOTJTI 


[WEST 


Wi 


car 


NORTI 


3WEST 


HORE 
SUR 


jONTAL 
PACT 


I 


IG 


/ 


IG 


I 


IG 


J 


'o 


" 7 


IG 


/ 


IG 


7 


IG 


7 


IG 


4:461 







































5:od 9 


8 


9 


8 


3 


2 


















0.01 


0.007 


6:00! 67 


58 


72 


63 


35 


26 


















15 


8 


7:00 142 


120 


174 


152 


103 


78 


















77 


53 


8:00! 150 


120 


209 


181 


145 


114 


















151 


120 


































9:00 118 
10:00 60 


83 
32 


191 
143 


157 
104 


154 
139 


118 
101 


26 

55 


8 
27 














214 
264 


181 
230 


11:00 2 


0.1 


75 


43 


103 


67 


72 


41 














291 


256 


12:00 








55 


28 


78 


46 


55 


28 










300 


265 


l:oJ 












72 


41 


103 


67 


75 


43 


2 


0.1 


291 


256 


2:00 












55 


27 


139 


101 


143 


104 


60 


32 


264 


230 


3:00! 












26 


8 


154 


118 


191 


157 


118 


83 


214 


181 


4:00| 
















145 


114 


209 


181 


150 


120 


151 


120 


5:00; 
















103 


78 


174 


152 


142 


120 


77 


53 


6:00! 
















35 


26 


72 


63 


67 


58 


15 


8 


7:00 
















3 


2 


9 


8 


9 


8 


0.01 


0.007 


7:14 









































152 



CHAPTER 8. COOLING LOAD 



TABLE 4. SOLAR RADIATION IMPINGING AGAINST WALLS HAVING SEVERAL ORIENTATIONS 

AND A HORIZONTAL SURFACE, AND THE RADIATION TRANSMITTED THROUGH GLASS 

FOR THE SAME ORIENTATIONS 

For 40 Deg Latitude on the twenty-first of July, in Bin per sqft per hour. 



SUN 
TIME 


NORTHEAST 


EAST 


SOUTHEAST SOUTH SOUTHWEST WEST ISORTI 


, HORIZONTAL 
IWEST i SURFACE 


T 




















j. 


G 










/ G , J 


J G L 


J G 7 


7 G l 


'G 


4:31 








: ' 




\ 


5:00, 14 


12 


14 


12 


- 


3 i ; ; 




1 1 


0.2 


6:00 


72 


63 


80 


70 


40 29 








19 11 


7:001 143 


120 


180 


158 


112 


87 








; 82 


57 


8:00 143 


111 


211 


182 


155 


124 


8 


2 






152 


121 


9:00 


104 


69 


192 


158 


168 


133 


46 


22 


| 




] 




213 


178 


10:00 


46 


22 


143 


104 


156 


117 


77 


45 


! 




j 




255 


225 


11:00 






75 


43 


121 


83 


95 


60 


15 , 4 




i 


284 


249 


12:00 










73 


42 


103 


67 


73 1 42 










293 


258 


1:00 










15 


4 


95 


60 


121 


83 


75 


43 






284 


249 


2:00 














77 


45 


156 


117 


143 


104 


46 


22 


25S 


225 


3:00 














46 


22 


168 


133 


192 


158 


104 


69 


213 


178 


4:00 














8 


2 


155 


124 


211 


182 


143 


111 


152 


121 


5:00 
















112 


87 


180 


158 


143 


120 


82 


57 


6:00 










i 






40 


29 


80 


70 


72 


63 


19 


11 


7:00 














5 3 


14 


12 


14 


12 


1 


0.2 


7:29 






























o 


























1 













TABLE 5. SOLAR RADIATION IMPINGING AGAINST WALLS HAVING SEVERAL ORIENTATIONS 

AND A HORIZONTAL SURFACE, AND THE RADIATION TRANSMITTED THROUGH GLASS 

FOR THE SAME ORIENTATIONS 

For 45 Deg Latitude on the twenty-first of July, in Btu per sqft per hour. 



SUN 
TIME 


NORTHEAST 


EAST 


SOUTHEAST 


SOUTH 


SOUTHWEST 


WEST 


NOETHWEST 


HORIZONTAL 

SUMACS 


J 


*G 


J 


*G 


J 


'G 


J 


*G 


7 


'G 


I 


'G 


I 


*G 


r 


*G 


4:26 










































5:00 


25 


22 


24 


21 


9 


6 


















2 


07 


6:00 


89 


77 


99 


88 


52 


39 


















26 


15 


7:00 


149 


125 


194 


170 


125 


99 


















90 


63 


8:00 


140 


109 


219 


189 


171 


139 


22 


8 














156 


123 


9:00 


92 


58 


194 


160 


183 


148 


65 


36 














210 


177 


10:00 


33 


13 


144 


106 


171 


134 


98 


63 














251 


217 


11:00 






75 


43 


139 


101 


121 


83 


32 


13 










274 


240 


12:00 










91 


67 


128 


90 


91 


67 










282 


247 


1:00 










32 


13 


121 


83 


139 


101 


75 


43 






274 


240 


2:00 














98 


63 


171 


134 


144 


106 


33 


13 


251 


217 


3:00 














65 


36 


183 


148 


194 


160 


92 


58 


210 


177 


4:00 














22 


8 


171 


139 


219 


189 


140 


109 


156 


123 


5:00 


















125 


99 


194 


170 


144 


125 


90 


63 


6:00 


















52 


39 


99 


88 


89 


77 


26 


15 


7:00 


















9 


6 


24 


21 


25 


22 


2 


0.7 



153 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



transmitted through a surface depends upon the nature of the exterior 
surface of wall or roof construction, it is necessary, in order to determine 
actual amount of solar heat transmission, to apply correction factors to 
the values of (I). Solar radiation factors and solar absorption coefficients 
have been determined 3 as indicated in Fig. 2 and Table 6 respectively. 



0.20 



0.18 



0.14 



U.Q.I: 

I 

SL. 



-U 



C0.08 



0.06 



0.04 



0.02 



0.1 O2 O3 O4 O5 O6 07 

WALL TRANSMISSION COEFFICIENT, Uw 

FIG. 2. SOLAR RADIATION FACTORS 



.8 



The solar heat conduction through a wall or roof exposed to the sun 
may be expressed by the formula: 



- A Fal 



(2) 



where 



HR Solar heat transmission, Btu per hour. 
A - Area of wall or roof, square feet. 

F = Percentage (expressed as a decimal) of the absorbed solar radiation which is 

transmitted to the inside (Fig. 2) . 
a = Percentage (expressed as a decimal) of the incident solar radiation which is 

absorbed by the surface (Table 6). 
/ - Actual intensity of solar radiation striking surface. Btu per hour per square 

foot (Tables 2 r 3, 4 and 5). 



*A Rational Heat Gain Method for the Determination of Air Conditioning Cooling Loads, by F. H. 
Faust, L. Levine and F. 0. Urban (A.S.H.V.E. TRANSACTIONS, Vol. 41. 1935? 327)7 

154 



CHAPTER 8. COOLING LOAD 



The total amount of heat conducted through a wall exposed to the sun 
is the sum of Ht and H& from Formulas 1 and 2. 

The calculation of heat transmission through walls and roofs does not 
take into consideration the heat capacity of the structure nor the con- 

TABLE 6. SOLAR ABSORPTION COEFFICIENTS FOR DIFFERENT BUILDING MATERIALS 



SURFACE MATERIAL 



ABSORPTION COEFFICIENT 

(a) 



Very Light Colored Surfaces 
White stone 

Very light colored cement 
White or light cream-colored paint 



0.4 



Medium Dark Surfaces 
Asbestos shingles 
Unpainted wood 
Brown stone 
Brick and red tile 
Dark-colored cement 
Stucco 
Red, green or gray paint 



0.7 



Very Dark Colored Surfaces 
Slate roofing 
Tar roofing materials 
Very dark paints 



0.9 



sequent time lag in the transmission of heat. In the case of massive walls 
the time lag may amount to several hours 4 . Thus in many cases the wall 
transmission cannot be added directly to the cooling load from dther 
sources because the peak of the wall transmission load may not coincide 

TABLE 7. TIME LAG IN TRANSMISSION OF SOLAR RADIATION THROUGH WALLS AND ROOFS 



TYPE AND THICKNESS OF WAIJ. OB ROOF 


Tom LAG, 
HOTJHS 


2-in. oine 


\Yz 


i*i. ^.*^^- - 

o-in. concrete 


3 


4rin. gypsum 


2^ 


3-in. concrete and 1-in. cork. . ~ 


2 


2-in. iron and cork (equivalent to %-in. concrete and 2.15-in. cork) 
4-in. iron and cork (equivalent to 5J^-in. concrete and 1.94-in. cork) . , . 


2^ 
7H 


8-in. iron and cork (equivalent to 16-in. concrete and 1.53-in. cork) 


19 


22-in. brick and tile wall 


10 







with the peak of the total cooling load and may even occur after the 
cooling system has been shut down for the day. The data in Table 7 were 
taken from A.S.H.V.E. research papers and whereas they result from a 
study of experimental slabs, they give an approximate idea of the time lag 
to be expected in various structures. 



<Loc. Cit. Notes 1 and 2. 



155 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Sun Effect Through Windows 

Windows present a problem somewhat different from that of opaque 
walls, because they permit a large percentage of the solar^ energy to pass 
through undiminished ; only a small percentage (approximately 10 per 
cent) is reflected. This fact permits the solar heat gain through windows 
to be expressed by the simple formula: 



where 



(3) 



HG = Solar radiation transmitted through a window, Btu per hour. 
^G = Area of glass, square feet. 

^G Amount of solar radiation transmitted directly through the glass, Btu per hour 
per square foot (Tables 2, 3, 4 and 5). 

Values for solar heat transmission through glass as determined by 
Formula 3 apply only to unshaded windows. Tests at the A.S.H.V.E. 
Research Laboratory* have determined the percentages of heat from 
solar radiation actually delivered to a room with bare windows and with 
various types of outdoor and indoor shading. The data in Table 8 are 
taken from these tests. 

TABLE 8. SOLAR RADIATION TRANSMITTED THROUGH BARE AND SHADED WINDOWS 



TTPB OF APPUBTENANCB 


FINISH 
FACING 

SUN 


PEB CENT 
TO ROOM 


Bare window glass.. .. 




97 


Canvas awniner . 


Plain 


28 


Canvas awning 


Aluminum 


22 


Inside shade, fully drawn 


Aluminum 


45 


Inside shade, one-half drawn . . 


Buff 


68 


Inside Venetian blind, fully covering window, slats at 45 deg 
Outside Venetian blind, fully covering window, slats at 45 deg.... 


Aluminum 
Aluminum 


58 
22 



The percentage values in this table were obtained by dividing the total 
amount of heat actually entering through the shaded window by the total 
amount of heat calculated to enter through a bare window (solar radiation 
plus glass transmission based on observed outside glass temperature). 
For bare windows on which the sun shines, the transmission of heat from 
outside air to glass is small or negative because the glass temperature is 
raised by the solar radiation absorbed. Therefore, in calculating the 
total heat gain through windows on the sunny sides of buildings, it is 
sufficiently accurate to determine the total cooling load due to the win- 
dow, as the solar radiation times the proper factor from Table 8 and to 
neglect the heat transmission through the glass caused by the difference 
between the temperatures of the inside and outside air. 

Although Table 8 shows that 97 per cent of the heat from solar radia- 
tion is delivered to a room through bare window glass, more recent tests 6 



*Radiation of Energy Through Glass, by J. L. Blackshaw and F. C. Houghten (A.S.H.V.E. TRANS- 
ACTIONS, Vol. 40, 1934, p. 93). Studies of Solar Radiation Through Bare and Shaded Windows, by F. C. 
Houghten, Carl Gutberlet, and J. L. Blackshaw (A.S.H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 101). 

Cooling Requirements of Single Rooms in a Modern Office Building, by F. C. Houghten, Carl Gutberlet, 
and Albert J. Wahl (A.S.H.V.E. TRANSACTIONS, Vol. 41, 1935, p. 53). 

156 



CHAPTER 8. COOLING LOAD 



have indicated that in the case of a building having floors of high heat 
capacity such as concrete floors on which the solar radiation falls, approxi- 
mately one-half of the heat entering a bare window is absorbed by the 
floor and does not immediately become a part of the cooling load but is 
delivered back to the air in the building at a slow rate over a period of 
24 hours or longer. 

The maximum solar intensity on any surface is of limited duration as 
shown in Fig. 1. In the case of windows the total energy impinging on the 
glass before and after the time of maximum intensity is further reduced 
by increased shading^ of the glass from the frame, or wall. The cooling 
load due to solar radiation therefore does not have to be calculated as a 
steady load. Another point which should be noted is that the maximum 
solar radiation load on the east wall occurs early in the morning when the 
outside temperature is low. 

In a paper 7 by the A.S.H.V.E. Research Laboratory it was shown that 
ordinary double strength window glass transmits no measurable amount 
of energy radiated from a source at 500 F or lower; that it transmits only 
6.0 and 12.3 per cent of the total radiation from surfaces at 700 F and 
1000 F, respectively; and that it transmits 65.7 per cent of the radiation 
from an arc lamp, 76.3 per cent of the radiation from an incandescent 
tungsten lamp, and 89.9 per cent of the radiation from the sun. Thus, 
glass windows in a room constitute heat traps, which allow rather free 
transmission of radiant energy into the room from the sun to warm objects 
in it, but do not allow the transmission of re-radiated heat from these 
same objects. 

Tests have been made which indicated that sunshine through window 
glass is the most important factor to contend with in the cooling of an 
office building. At times it was shown to account for as much as 75 per 
cent of the total cooling necessary. Because of the importance of the 
sunshine load, cooling systems should be zoned so that the side of the 
building on which the sun is shining can be controlled separately from the 
other sides of the building. If buildings are provided with awnings so 
that the window glass is shielded from sunshine, the amount of cooling 
required will be reduced and there will also be less difference in the cooling 
requirements of different sides of the building. The total cooling load 
for a building exposed to the sun on more than one side is of course less 
than the sum of the maximum cooling loads in the individual rooms since 
the maximum solar radiation load on the different sides occurs at different 
times. In determining the total cooling load for a building if the time 
when the maximum load occurs is not obvious, the load should be calcu- 
lated for various times of day to determine the times at which the sum 
of the loads on the different sides of the building is a maximum. 

Heat Emission of Occupants 

The heat and moisture given off by human beings under various states 
of activity are shown in Figs. 8 to 11 and Table 4 of Chapter 3. It will be 
observed that the rate of sensible and latent heat emission by human 
beings varies greatly depending upon state of activity. In many applica- 
tions this component becomes a large percentage of total load. 

Txx:. Cit. Note 5. 

157 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

Heat Introduced by Outside Air 

An allowance must be made for the heat and moisture in the outside 
air introduced for ventilation purposes or entering the building through 
cracks, crevices, doors, and other places where infiltration might occur. 

The volume of air entering due to infiltration may be estimated from 
data given in Chapter 6. Information on the amount of outside air 
required for ventilation will be found in Chapter 3 . 

In the event the volume of air entering an enclosure due to infiltration 
exceeds that required for ventilation, the former should be used as a basis 
for determining the portion of the load contributed by outside air. Where 
volume of air required for ventilation exceeds that due to infiltration it is 
assumed that a slight positive pressure will exist within the enclosure with 
a resulting exfiltration instead of infiltration. In this case the air required 
for ventilation is used in determining outside air load. 

The sensible heat gain resulting from the outside air introduced may be 
determined by the following formula: 

H s = 0.24 X 60 do Q (to - (4) 

where 

H s sensible heat to be removed from outside air entering the building, Btu per hour. 

Q = volume of outside air entering building, cubic feet per minute. 

do - density of air, pounds of dry air per cubic foot at temperature t . 

to = temperature of outside air, degrees Fahrenheit. 

t = temperature of inside air, degrees Fahrenheit. 

The total heat gain resulting from outside air introduced may be deter- 
mined by the following formula: 

H = 60 do Q (h - h) (5) 

where 

H total heat to be removed from outside air entering the enclosure, Btu per hour. 
Q = volume of outside air entering enclosure, cubic feet per minute. 
do = density of air, pounds of dry air per cubic foot of air (at temperature / ). 
fio = heat content of mixture of outside dry air and water vapor, Btu per pound of 

dry air (at temperature t ). 
h = heat content of mixture of inside dry air and water vapor, Btu per pound of 

dry air (at temperature t). 

The latent heat gain resulting from outside air introduced may be 
determined by the following formula: 

Hi = H - H n (6) 

where 

Hi - latent heat to be removed, Btu per hour. 
H total heat to be removed, Btu per hour. 
H s = sensible heat to be removed, Btu per hour. 

Heat Emission of Appliances 

Heat generating appliances which give off either sensible heat or both 
sensible and latent heat in an air conditioned enclosure may be divided 

158 



CHAPTER 8. COOLING LOAD 



into three general classes of equipment or devices: 

1. Electrical appliances. 

2. Gas appliances. 

3. Steam heating appliances. 

In the first group may be found such devices as lights, motors, toasters, 
waffle irons, etc. The capacities of most electrical devices may be 
determined from the watt capacity indicated on their^ name plates. 
The Btu equivalent of heat generated per hour is determined by multi- 
plying the watt capacity by 3.4 (one watthour is equivalent to 3.413 btu). 

The capacities of electric motors are usually expressed in terms of 
horsepower instead of watts. If the motor efficiency is known, the watts 
input may be calculated from the formula: 

= 746 (hp) ( 7) 

n 

where 

P = motor input, watts. 
hp motor load, horsepower. 
n = motor efficiency (expressed as a decimal). 

When the motor efficiency is not known the heat equivalent of e j? c ^ ic ?; 1 
input can be approximately determined by applying data given in 1 able V>. 

HEAT GENERATED BY MOTORS 



NAMEPLATE EATING HORSEPOWER 


TTHUT GAIN IN BTTJ PEE HOUR PEE HORSEPOWER 


Connected Load in Same Room 


Connected Load Outside of Room 


Ysto % 
Hto3 
3 to 20 


4250 
3700 
2950 


1700 
1150 
400 



In the second group belong such appliances as coffee urns, gas ranges, 
sten tables, broilers, hot plates, etc. For heat generating capacities 
of such appliances refer to Table 10. 

Considerable judgment must be exercised in the use of data given in 
Table 10. Consideration must be given to time of day when appliances 
are used and the heat they contribute to the space at time of peak .load. 
Only those appliances in use at the time of the peak load need be con- 
sidered. Consideration must also be given to the way appliances ar 
installed, whether products of combustion are vented to a flue, whethe 
products of combustion escape into the space to be conditioned or whethe 
appliances are hooded allowing part of the heat to escape through 
stSk?onnected with the hood. There are no generally acceptoi dafe 
available on the effects of venting and shielding heating appliances but i 
TbeSed tiiat when the appliances are properly hooded wi* a pomtij 
fan exhaust system through the hood that 50 per cent of the heat will b^ 
SnvSed up SS the hood and the balance of 50 per cent will be dissipate. 
S the Sac? to be conditioned. Where latent as well as sensible heat i 
Sv?n off, h is usually safe to assume that all latent heat will be remove, 
by a properly designed and operated vent or hood. 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 


TABLE 10. 


HEAT GAIN FROM VARIOUS SOURCES 




SOURCE 


BTU PK. 


s. HOUR 


Sensible La 


tent Total 



Electric Heating Equipment 






Electrical Equipment Dry Heat No Evaporated \\ ater _ - 
Electric Oven Baking - 
Electric Equipment Heating Water Stewing, Boiling, etc 
Electric Lights and Appliances per Watt (Dry Heat)_ 
Electric Lights and Appliances per Kilowatt (Dry Heat) 
Electric Motors per Horsepower 


100% 
80% 
50% 
3.4 
3413 
2546 
90% 

1200 
600 
* 
* 
8000 
1025 
300 
850 
3200 
* 
* 
2050 
2050 


0% 
20% 
50% 



10% 
2000 
1200 
600 

* 
2000 

800 

1300 
* 
* 




100% 
100% 
100% 
3.4 
3413 
2546 
100% 

2400 
1200 
3400 
7500 
10000 
1025 
1100 
850 
4500 
4600 
9000 
2050 
2050 


Coffee Urn Large, IS in. Diameter Single Drum. - 


Coffee Urn Approx. Connected Load per Gallon of Capacity 
Electric Range Small Burner. 

Electric Range"" Large Burner - ....... ~ ...........-. 


Electric Range Oven.. - - 

Electric Ra.nze AVarming Compartment ....... ,- -,., .. 


Steam Table Per Square Foot of Top Surface 


Baker's Oven Per Cubic Foot of Volume . --. ............. ...... ...*....... 


Frying Griddles Per Square Foot of Top Surface 


Hair Dryer in Beauty Parlor ^600 w 

Permanent Wave Machine in Beauty Parlor 24-25 w Units 


Gas Burning Equipment 


Gas Equipment Dry Heat No Water Evaporated 
Gas Heated Oven Baking. . -. 


90% 
67% 
50% 

12000 
5000 

* 
* 
5000 
3000 
500 
2500 
400 
540 
2250 
2250 

4500 
2250 
900 
540 
135 


10% 
33% 
50% 

6000 
5000 

* 
* 
5000 
3000 
500 
2500 
900 
60 
250 
250 

500 
250 
100 
60 
15 


100% 
100% 
100% 
10000 
18000 
10000 
12000 
10000 
18000 
250 
100000 
100 
250 
2500 
10000 
6000 
1000 
5000 
1300 
600 
2500 
2500 
5000 
3000 
3000 
1800 
3000 
1800 
5000 
3000 
5000 
2500 
1000 
600 
150 


Gas Equipment Heating Water Stewing, Boiling, etc 
Stove, Domestic Type No Water Evaporated Per Medium Size Burner. 
Gas Heated Oven* Domestic Type - 


Stove Domestic Type Heating Water Per Medium Size Burner ... - - 


Residence Gas Range Giant Burner (About 5J^j in. Diameter*) .. ,- 


Residence Gas Range Medium Burner (About 4 in, Diameter) ,.., 


Residence Gas Range Double Oven (Total Size 18 in. x 18 in. x 22 in. High) 
Residence G&s Range "Pilot . ...... ....... ...,,-,- , T ,-, 


Restaurant Range 4 Burners and Oven _. 


Cast-iron Burner Low Flame Per Hole....- ~ 


Cast-iron Burner High Flame Per Hole. .. 


Sinnneritjg Burner - ............ 


Coffee Urn Large, 18 in. Diameter Single Drum 


Coffee Urn Small," 12 I'TV Diameter Single PT 


Coffee Urn Per Gallon of Rated Capacity .. .-. 


Egg Boiler Per Egg Compartment 


Steam Table or Serving Table Per Square Foot of Top Surface ,.- ... r ,,_ 


Dish Warmer Per Square Foot of Shelf,- ^ ,- -, - -* 


Cigar Lighter Continuous Flame Type- - 


Curling Iron Heater ~ - 


Bunsen Type Burner Large Natural Gas 


Bunsen Type Burner~ Large- Artificial Gas..................... ................... .............. 
Bunsen Type Burner~~SmalV~~Natural Gas 


Bunsen Type Burner Small Artificial Gas -,- ,-,--,- 


Welsbacli "Burner Natural Gas 


Welsbach Burner Artificial Gas 


Fish-tail Burner Natural Gas , .,....,, ^ -, --, -, - T 


Fish-tail Burner Artificial Gas. . . 


Lighting Fixture Outlet Large, 3 Mantle 480 C.P 


Lighting Fixture Outlet Small, 1 Mantle 160 C.P 


One Cubic Foot of Natural Gas Generates 


One Cubic Foot of Artificial Gas Generates 


One Cubic Foot of Producer Gas Generates- _ 



Steam Heated Equipment 



Steam Heated Surface Not Polished Per Square Foot of Surface 
Steam Heated Surface Polished Per Square Foot of Surface 


330 
130 
80 
400 
220 
110 
2000 
1200 
2500 
300 








2000 
1200 
2500 
800 


330 
130 
80 
400 
220 
110 
4000 
2400 
5000 
1100 


Insulated Surface, Per Square Foot .... ......... _... ...u.^. 
Bare Pipes, Not Polished Per Square Foot of Surface.- 


Bare Pipes, Polished i*er Square Foot of Surface. , 


Insulated Pipes, Per Square Foot . - 


Coffee Urn Large ( 18"in. Diameter "Single PniTTL 


Coffee Urn Small, 12 in. Diameter Single Drum 
Egg Boiler Per Egg Compartment .. ... 


Steam Table Per Square Foot of Top Surface 



Miscellaneous 



Heat Liberated By Food per person, as in a Restaurant 

Heat Liberated from Hot Water used direct and on towels per hour Barber Shops | 



30 
100 



30 
200 



60 
300 



'"Per cent sensible and latent heat depends upon use of equipment; dry heat, baking or boiling. 

160 



CHAPTER 8. COOLING LOAD 



GENERAL 

From the foregoing discussion it is obvious that the determination of 
the maximum cooling load is rather complicated by reason of the variable 
nature of contributing load components. If the time when the maximum 
load occurs is not obvious the load should be calculated for various times 
of the day to determine the probable time at which the sum of the various 
component loads is a maximum. 

Application of the foregoing data in determining cooling load require- 
ments is illustrated in Example 1. 



Store room 



/< - 




b 

fe 



Ceiling height, 12-V 



-54-'0"- 




8'x6' 14'x6' H'x6' 

FIG. 3. PLAN DIAGRAM OF CLOTHING STORE 



14'x6' 



Example 1. Determine cooling load requirements for a clothing store illustrated in 
Fig. 3 and located in Cleveland, Ohio, Latitude 40 deg. This is a one-story building 
located on a corner and it faces south and west. Assume building on east and north 
sides conditioned. 

Wall construction, 8 in. hollow tile, 4 in. brick veneer, plaster on walls, U = 0.33 
(Table 4, Wall 38 B, Chapter 5). 

Roof construction, 2 in. concrete, % in. rigid insulation, metal lath and plaster 
ceiling, U = 0.26 (Table 11, Wall 2 J, Chapter 5). 

Floor, maple flooring on yellow pine, no ceiling below, U = 0.34 (Table 8, Wall 

1 D, Chapter 5). 

Partition, wood lath and plaster on both sides of studding, U = 0.34 (Table 6, 

Wall 77 B, Chapter 5). 

Show windows, provided with awnings and thin panel partition at rear. 

Front doors, 2 ft 6 in. x 7 ft (glass panelled), U - 1.13 (Table 13 A, Chapter 5). 

Side door, 3 ft x 7 ft (solid, 1% in. thick), U = 0.51 (Table 13 B, Chapter 5), 

Occupancy, 10 clerks, 40 patrons. 

Lights, 4200 w. 

Outside design conditions, dry-bulb 95 F; wet-bulb 75 F. 

Inside design conditions, dry-bulb 80 F; wet-bulb 67 F. 

Basement temperature, 85 F. 

Store room temperature, 88 F. 

161 



HEATING VENTHATINO AIR CONDITIONING GUIDE 1938 



Solution: The normal heat transmission through various surfaces shown in load 
calculations are determined by application of Formula 1. 

It is quite obvious from the shape and exposure of this store that the maximum sun 
load will exist on the west wall. Since the west wall has a large glass area with a negligible 
time lag, the peak load may be expected at 4:00 p.m. at which time, from Table 4, 
IG - 182. JG f r south glass at 4:00 p.m. is 2. Because of the small amount of solar 
radiation transmitted through the south glass, the transmission due to temperature 
difference has also been included. Assuming time lag in roof and walls to be 2 hours, the 
corresponding values for 7 for south and west walls and roof will be those shown in Table 
4 for 2:00 p.m. They are respectively 77, 143 and 258. A time lag of 1 hour was assumed 
for the west door amounting to I = 192. By substituting these values in equations 2 
and 3 the solar heat load is determined. 

To determine the heat gain from the outside air it is necessary first to determine the 
volume of the outside air to be introduced. Since the show windows are sealed so as not 
to permit infiltration and since there are only three doors in this store through which 
infiltration can take place, it is obvious that infiltration of air will be a negligible quan- 
tity. The volume of the store is 21,600 cu ft. Good practice indicates that in a store 
of this character there should be a minimum of from ltol% outside air changes per hour. 
On a basis of 1}4 air changes the volume of outside air to be ^introduced would be 32,400 
cfh. By reference to Chapter 3 it will be noted that the minimum ventilation require- 
ments are 10 cfm per person. On this basis the ventilation requirements would be 
30,000 cfh. Since this will produce approximately IJi outside air changes per hour, 
30,000 cfh will be considered in this application. 

To determine load imposed by occupants it will be found from Table 4, Chapter 3 
that the average person standing at rest will dissipate 225 Btu sensible heat and 206 
Btu latent heat per hour. 

NORMAL TRANSMISSION LOAD: 



SURFACE 


DIMENSIONS 


AREA 

SQ FT 


U 


TEMP. DIFF. 
DEGP 


BTTJ PBB 
HOUR 


S Glass 

S Wall 
W Wall 
WDoor 
Roof 
Floor 
N Partition 

Total 


2(2 ft 6 in. x 7ft) + 
2(10 ft x 6 ft) 
(30 ft x 12 ft) -155 
(GO ft x 12 ft) -321 
3 ft x 7 ft 
60 ft x 30 ft 
26 ft x 54 ft 
30 ft x 12 ft 


155 
205 
399 
21 
1800 
1404 
360 


1.13 
0.33 
0.33 
0.51 
0.26 
0.34 
0.34 


15 
15 
15 
15 
15 
5 
8 


2,627 
1,015 
1,975 
161 
7,020 
2,387 
979 


16,164 



SUN LOAD: 



SURFACE 


DIMENSIONS 


AREA 

SQ FT 


. F 


a 


JOB 
*G 


SHADE 
FACTOR 


BUT PEE 
HOUR 


SWall 
S Glass 
W Glass 

WDoor 
W Wall 
Roof 

Total 


3(14 ft x 6 ft) + 
(8 ft x 6 ft) 


205 
155 

300 
21 
399 
1800 


0.078 

0.118 
0.078 
0.062 


0.7 

0.7 
0.7 
0.9 


77 
2 

182 
192 
143 
258 


0.28 
0.28 


862 
87 

15,288 
333 
3,113 
25,914 


45,597 



OUTSIDE AIR HEAT GAIN: 

Sensible heat, H s = 0.24 X 60 d Q (t Q - f) (Formula 4). 
Q = 50 X 10 = 500 cfm. 

Density of air at 95 F dry-bulb and 75 F wet-bulb for a barometric pressure of 29.92 in. 
is 0.07089 Ib per cubic foot (Table 4, Chapter 1). 

Dew-point of outdoor air is 66 F (psychrometric chart). 

162 



CHAPTER 8. COOLING LOAD 



Partial pressure of vapor is 0.64378 in. Hg. (Pressure of saturated vapor at 66 F, 
Table 6, Chapter 1). 



a622 



- 622 



= a 137 lb water vapor per 



pound dry air (Formula 5 a, Chapter 1). 
- : - n nlQ - = 0.986 lb dry air per pound outside air. 

1 plUS U.Uloi 

do = 0.07089 X 0.986 = 0.0699 lb dry air per cubic foot outside air. 

H 6 =- 60 X 500 X 0.0699 X 0.24 (95-80) - 7549 Btu per hour. 

Total heat, H = 60 d Q Q (h - K) (Formula 5). 

h = 38.46 Btu per pound dry air at 75 F wet-bulb (Table 6, Chapter 1). 
h = 31.51 Btu per pound dry air at 67 F wet-bulb (Table 6, Chapter 1). 
H = 60 X 0.0699 X 500 (38.46 - 31.51) = 14,574 Btu per hour. 

Latent heat gain from outside air = 14,574 7549 = 7025 Btu per hour. 
PEOPLE HEAT GAIN: 

50 X 225 = 11,250 Btu per hour, sensible heat. 

50 X 206 = 10,300 Btu per hour, latent heat. 
LIGHT HEAT GAIN: 

4200 X 3.413 = 14,335 Btu per hour. 
SUMMARY: 



CQMPOHPSNT OF LQAI 


BTU FBI 


i HOUB 




Sensible 


Latent 


Normal Transmission Load .. 
Sun Load 


16,164 
45,597 




Outside Air Heat Gain.. 
People Heat Gain - - 
Light Heat Gain !_ ., 


7,549 
11,250 
14,335 


7,025 
10,300 


TotaL - 


94,895 


17,325 









TOTAL LOAD: 
94,895 + 17,325 



112,220 Btu per hour. 



PROBLEMS IN PRACTICE 

1 The outdoor and indoor temperatures are 90 F and 78 F, respectively. What 
is the amount of heat transmitted per hour through a 7 ft by 4 ft north window? 

H t = 28 X 1.13 (90-78) 380 Btu per hour. (Equation 1, Chapter 8 and Table 13 A, 
Chapter 5). 

2 a. If a restaurant has two 10 gal gas-heated coffee urns, what is the cooling 
load due to them? 

b. What is the cooling load due to four 1350 w burners on an electric range? 

a. 2 X 10 X 1000 = 20,000 Btu per hour (Table 10). 

b. 4 X 1350 - 5400 w - 5.4 kw. 

5.4 X 3413 = 18,430 Btu per hour (Table 10). 

3 a. What is the maximum heat transmission for a flat roof located in Pitts- 
burgh (latitude 40 deg) exposed to the sun with the outdoor and indoor tem- 

163 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



perature 95 F and 80 F, respectively? The roof is of uninsulated 6 in. concrete 
with its underside exposed, and -with a black upper surface. 

b. What time of day will maximum cooling load due to the roof exist? 

a. Ht + Hjt = [A U (t - t)] + [A Fal\ (Formulas 1 and 2). 
U for roof = 0,64 (Table 11, Wall 4 A, Chapter 5). 

F - 0.147 (Fig. 2). 

a - 0.9 (Table 6). 

/ = 293 (Table 4). 

Ht + HR = [1 X 0.64 (95-80)] + [1 X 0.147 X 0.9 X 293] 48.5 Btu per square 
foot per hour. 

b. Maximum sun intensity occurs at noon (Table 4). Maximum effect in cooling load 
will occur at 3 p.m. (Table 7). 

4 a. What is the maximum rate of heat delivered to a room through a hare 
window in the west wall of a building located in New Orleans (30 deg latitude)? 

h. What tune of day will it occur? 

c. What will maximum rate be if window is protected by awning? 

a. H G = A G !G (Formula 3). 
7 G = 177 (Table 2). 
HG = 1 X 177 = 177 Btu per square foot per hour. 

6. At 4 p.m. (Table 2). 

c. 177 X 0.28 = 49.6 Btu per square foot per hour (Table 8). 

5 What is the heat gain per cubic foot of outside air introduced, under the 
following conditions if the barometric pressure is 29.5 in. Hg.? 

Outdoor temperatures, 90 F dry-bulb and 75 F wet-bulb. 
Inside temperatures, 78 F dry-bulb and 65 F wet-bulb. 

Density of air at 90 F dry-bulb, 75 F wet-bulb and 29.5 in Hg. is 0.0705 Ib per cubic foot 
(Table 4, Chapter 1). 

Dew-point of outdoor air is 68.2 F (psychrometric chart). 

Pressure of saturated vapor at 68.2 F is 0.6946 in. Hg. (Table 6, Chapter 1). 

W - 0.622 (-JIT?) = 0.622 ( 29 S^QSQ^ ) " ' 15 lb water va P r P er P oun ^ dry 
air (Formula oa, Chapter 1). 

0.985 Ib dry air per pound outside air. 



j r- 

d = 0.0705 X 0.985 = 0.06944 Ib dry air per cubic foot outside air. 
Heat content outside dry air at 75 F wet-bulb = 38.46 Btu per pound. 
Heat content inside dry air at 65 F wet-bulb = 29.96 Btu per pound. 
Total heat, H 0.06944 (38.46 - 29.96) = 0.59 Btu per cubic foot. 

6 A 7 X 4 ft west window is equipped with an inside aluminum finished 
Venetian blind which is adjusted to fully cover the window when the sun shines. 
The^net glass area is 75 per cent of the total area of the window. What is the 
cooling load due to the window at 10 a.m. and 4 p.m.? Temperatures are: 
10 a.m., outside 85 F and inside 77 F; 4 p.m., outside 95 F and inside 80 F. 
Latitude 40 deg. 

10 a.m.: Ht = 28 X 1.13 (85-77) = 253 Btu per hour (Equation 1, and Table 13A, 
Chapter 5). 

4 p.m.: 28 X 0.75 = 21 sq ft net glass area. 

H G * 21 X 182 X 0.58 = 2217 Btu per hour (Tables 4 and 8). 

164 



Chapter 9 

FUELS AND COMBUSTION 

Classification of Coal, Air for Combustion, Draft Required, 

Combustion of Anthracite, Firing Bituminous Coal, Burning 

Coke, Hand Firing, Classification and Use of Oil, Classification 

and Use of Gas 

THE choice of fuel for heating is a question of economy, cleanliness, 
fuel availability, operation requirements, and control. The principal 
fuels to be considered are coal, oil, and gas. 

CLASSinCATION OF COALS 

The complex composition of coal makes it difficult to classify it intc 
clear-cut types. Its chemical composition is some indication but coals 
having the same chemical analysis may have distinctly different burning 
characteristics. Users are mainly interested in the available heat pei 
pound of coal, in the handling and storing properties, and in the burning 
characteristics. A description of the relationship between the qualitiei 
of coals and these characteristics requires considerable space; a treatmen 
applicable to heating boilers is given in U. S. Bureau of Mines Bulletin 276 

A classification of coals is given in Table 1, and a brief description of th< 
kinds of fuels is given in the following paragraphs, but it should b 
recognized that there are no distinct lines of demarcation between th 
kinds, and that they graduate into each other: 

Anthracite is a clean, dense, hard coal which creates very little dust in ^ handling. ^ '. 
is comparatively hard to ignite but it burns freely when well started. It is non-cakin! 
it burns uniformly and smokelessly with a short flame, and it requires little attention 1 
the fuel beds between firings. It is capable of giving a high efficiency in the commc 
types of hand-fired furnaces. A tabulation of the quality of the various anthraci 
sizes will be found in U. S. Bureau of Mines Report of Investigations No. 3283. 

Semi-anthracite has a higher volatile content than anthracite, it is not as hard ax 
ignites somewhat more easily; otherwise its properties are similar to those of anthracit 

Semi-bituminous coal is soft and friable, and fines and dust are created by handling 
It ignites somewhat slowly and burns with a medium length of flame.^ Its caking pr 
perties increase as the volatile matter increases, but the coke formed is relatively wea 
Having only half the volatile matter content of the more abundant bituminous coals 
can be burned with less production of smoke, and it is sometimes called smokeless co 

The term bituminous coal covers a large range of coals and includes many types havi 
distinctly different composition, properties, and burning characteristics. The coals rat 
from the high-grade bituminous coals of the East to the poorer coals of the West. Th 
caking properties range from coals which completely melt, to those from which 1 
volatiles and tars are distilled without change of form, so that they are^ classed as n< 
caking or free-burning. Most bituminous coals are strong and non-friable enough 
permit of the screened sizes being delivered free from fines. In general, they ign 

165 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

easily and burn freely ; the length of flame varies with different coals, but it is long. Much 
smoke and soot are possible especially at low rates of burning. 

Sub-bituminous coals occur in the western states; they are high in moisture when 
mined and tend to break up as they dry or when exposed to the weather; they are liable 
to ignite spontaneously when piled or stored. They ignite easily and quickly and have a 
medium length flame, are non-caking and free-burning; the lumps tend to break into 
small pieces if poked; very little smoke and soot are formed. 

Lignite is of woody structure, very high in moisture as mined, and of low heating 
value; it is clean to handle. It has a greater tendency than the^sub-bituminous coals to 
disintegrate as it dries, and it also is more liable to spontaneous ignition. Freshly mined 
lignite, because of its high moisture, ignites slowly. It is non-caking. The char left after 
the moisture and volatile matter are driven off burns very easily, like charcoal. The 
lumps tend to break up in the fuel bed and pieces of char falling into the ashpit continue 
to burn. Very little smoke or soot is formed. 

Coke is produced by the distillation of the volatile matter from coal. The type of 
coke depends on the coal or mixture of coals used, the temperatures and time of distil- 
lation and, to some extent, on the type of retort or oven; coke is also produced as a 
residue from the destructive distillation of oil. 



TABLE 1. CLASSIFICATION OF COALS BY RANK/ 
Legend: F.C. = Fixed Carbon. V.M. = Volatile Matter. Btu = British thermal units. 



CLASS 


GEOUP 


LIMITS o? FECED CARBON OR BTU 
MINERAL-MATTER-FRBZ BASIS 


REQUISITE PHYSICAL 
PROPERTIES 




i. Meta-anthracite 


Dry F.C., 98 per cent or more (Dry 








V.M., 2 per cent or less) 




I. Anthracite 


2 Anthracite 


Dry F.C., 92 per cent or more and less 
than 98 per cent (Dry V.M., 8 per 
cent or less and more than 2 per cent) 
Dry F.C., 86 per cent or more and less 
than 92 per cent (Dry V.M., 14 per 


Non-agglutinating 


3 Semi-anthracite 








cent or less and more than 8 per cent) 






1 Low volatile bituminous coal 


Dry F.C., 77 per cent or more and less 








than 86 per cent (Dry V.M., 23 per 








cent or less and more than 14 per 








cent) 






2. Medium volatile bituminous coal 


Dry F,C., 69 per cent or more and less 
than 77 per cent (Dry V.M., 31 per 








cent or less and more than 23 per 




I^_ Bituminous ' 




cent) 






3. High volatile A bituminous coal. 


Dry F.C., less than 69 per cent (Dry 
V.M., more than 31 per cent); and 








moist 6 Btu, 14,000* or more 






4. High volatile B bituminous coal.. 


Moist* Btu, 13,000 or more and less 








than 14,000* 






5 High volatile C bituminous coal- 


Moist Btu, 11,000 or more and less 
than 13,000* 


Either agglutinating 
or non-weathering* 


f 


I. Sub-bituminous A coal 


Moist Btu, 11,000 or more and less 


Both weathering and 


| 




than 13,000* 


non-agglutinating 


III. Sub-bituminous., 


2. Sub-bituminous B oo^-l ..,_ .... , 


Moist Btu 9500 or more and less 
than 11,000* 






3. Sub-bituminous C coal 


Moist Btu 8300 or more and less 








than 9500* 






:1 T lignite 


Moist Btu less than 8300 


Consolidated 




2 "Rro^ra coal . ri 


Moist Btu less than 8300 


Unconsolidated 





If agglutinating, classify in low-volatile group of the bituminous class. 

*Moist Btu refers to coal containing its natural bed moisture but not including visible water on the 
surface of the coal. 

Pending the report of the Subcommittee on Origin and Composition and Metbods of Analysis, it is 
recognized that there may be non-caking varieties in each group of the bituminous class. 

*Coals having 69 per cent or more fixed carbon on tbe dry, mineral-matter-free basis shall be classified 
according to fixed carbon, regardless of Btu. 

There are three varieties of coal in the Higb- volatile C bituminous coal group, namely, Variety 1, 
agglutinating and non-weathering; Variety 2, agglutinating and weathering; Variety 3, non-agglutinating 
and non-weathering. 

/Adapted from .4 .S.T.lf. Standards on Coal and Coke, p. 68, American Society for Testing Materials, 
Philadelphia, 1934. 

166 



CHAPTER 9. FUELS AND COMBUSTION 



High-temperature cokes. Coke as usually available is of the high-temperature type, 
and contains between 1 and 2 per cent volatile matter. High-temperature cokes are sub- 
divided into beehive coke of which comparatively little is now sola for domestic use, by- 
product coke, which covers the greater part of the coke sold, and gas-house coke. The 
differences among _ these three cokes are relatively small; their denseness and hardness 
decrease and friability increases in the order named. In general, the lighter and more 
friable cokes ignite and burn the more easily. 

Low-temperature cokes are produced at low coking temperatures, and only a portion 
of the volatile matter is distilled off. Cokes as made by various processes under develop- 
ment have contained from 10 to 15 per cent volatile matter. In general, these cokes 
ignite and burn more readily than high-temperature cokes. The properties of various 
low-temperature cokes may differ more than those of the various high-temperature cokes 
because of the differences in the quantities of volatile matter and because some may be 
light and others briquetted. 

The sale of petroleum cokes for domestic furnaces has been small and is generally 
confined to the Middle West. They vary in the amount of volatile matter they contain, 
but all have the common property of a very low ash content, which necessitates the 
use of refractory pieces to protect the grates from being burned. 

In order to obtain perfect combustion a definite amount of air is re- 
quired for each pound of fuel fired. A deficiency of air supply will result 
in combustible products passing to the stack unburned, An excess of air 
absorbs heat from the products of combustion and results in a greater loss 
of sensible heat to the stack. 

Total Air Required. The theoretical amount of air required per pound 
of fuel for perfect combustion is dependent upon the analysis of the fuel ; 

TABLE 2. POUNDS OF AIR PER POUND OF FUEL AS FIRED 



ANTHRACITE 


Con 


Sma-BrruMiNOTJS 


BlTUHINOTTS 


LlGNTTI 


9.6 


11.2 


11.2 


10.3 


6.2 



however, for estimating purposes the theoretical air required for different 
grades of fuel may roughly be taken from Table 2. An excess ^of about 
50 per cent over the theoretical amount is considered good practice under 
usual operating conditions. 

The amount of excess air, based upon the laws of combustion, can be 
determined by its relation to the percentage of CO* (carbon dioxide) in 
the products of combustion. This relationship is shown by the curves 
(Fig. 1) for high and low volatile coals and for coke. In hand-fired fur- 
naces with long periods between firings the combustion goes through a 
cycle in each period and the quantity of excess air present varies. 

Secondary Air. The division of the total into primary and secondary 
air necessary to produce the same rate of burning and the same excess air 
depends on a number of factors which include size of fuel, depth of fuel 
bed, and diameter of firepot. The ratio of the secondary to the primary 
air increases with decrease in the size of the fuel pieces, with increase in 
the depth of the fuel bed, and with increase in the area of the firepot; the 
ratio also increases with increase in rate of burning. 

Size of the fuel is a very important factor in fixing the quantity of 
secondary air required for non-caking coals. With caking coals it is not 

167 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



22 

20 
18 

o 

g 14 



' I I 



YV XjL 



\V\ 



Low-volatile . 
./bituminous coa 



J High - volatile _ 
'bituminous coal 



~~20 40 60 80 100 120 140 160 
EXCESS AIR, PER CENT 



FIG. 1* RELATION BETWEEN C0 3 AND EXCESS AIR IN GASES OF COMBUSTION 

so important because small pieces fuse together and form large lumps. 
Fortunately a smaller size fuel gives more resistance to air flow through 
the f uel^ bed and thus automatically causes a larger draft above the fuel 
bed, which draws in more secondary air through the same slot openings. 
In spite of this, ^a small size fuel requires a larger opening of the door 
slots; for a certain size for each fuel no slot opening is required, and for 
larger sizes too much excess air gets through the fuel bed. 

It is impossible to establish a single rule for the correct slot opening for 
all types and sizes of fuels and for all rates of burning. Furthermore, the 



s 




iflojlw 


























































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s 






























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* 


s 




^ 


























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/ 


? 




/ 


' 






















J 


/ 




/ 






/ 
























\ 


Y 


.> 


/ 






/ 










in 














/ 


w 


,<< 


7 




/ 


/ 








/ 
















/ 






/ 




>v 










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s 




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Sfc 


ttdc 


*ed 












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EATEOFBim 


NING, POUNDS PER SQ. FT. PBH HR. 

From U. S, Bureau of Mi 


nes. 



FIG. 2. RELATIVE AMOUNT OF FIRE DOOR SLOT OPENING REQUIRED IN A GIVEN 
FURNACE TO GIVE EQUALLY GOOD COMBUSTION FOR HIGH TEMPERATURE 
COKE OF VARIOUS SIZES WHEN BURNED AT VARIOUS RATES 

168 



CHAPTER 9. FUELS AND COMBUSTION 



size of slot opening is dependent on whether the ashpit damper is open 
or closed. It is better to have too much than too little secondary air; the 
opening is too small if there is a puff of flame when the firing door is opened. 
Fig. 2, taken from the 17. S. Bureau of Mines Report of Investigations 
No. 2980, shows the relationship of the slot opening, for a domestic fur- 
nace, to the size of coke and the rate of burning; these openings are with 
the ashpit ^damper wide open, and would be less if the available draft 
permits of its being partly closed. The same openings are satisfactory for 
anthracite. 

Bituminous coals require a large amount of secondary air during the 
period subsequent to a firing in order to consume the gases and to reduce 
the smoke. The smoke produced is a good indicator, and that opening is 
best which reduces the smoke to a minimum. Too much secondary air 
will cool the gases below the ignition point, and prove harmful instead of 
beneficial The following suggestions will be helpful: 

1. In cold weather, with high combustion rates, the secondary air damper should be 
half open all the time. 

2. In very mild weather, with a very low combustion rate, the secondary air damper 
should be closed all the time. 

3. For temperatures between very mild and very cold, the secondary air damper 
should be in an intermediate position. 

4. For ordinary house operation, secondary air is needed after each firing for about 
one hour. 

Draft Requirements 

The draft required to effect a given rate of burning the fuel as measured 
at the smokehood is dependent on the following factors: 

1. Kind and size of fuel. 

2. Combustion rate per square foot of grate area per hour. 

3. Thickness of fuel bed. 

4. Type and amount of ash and clinker accumulation. 

5. Amount of excess air present in the gases. 

6. Resistance offered by the boiler passes to the flow of the gases. 

7. Accumulation of soot in the passes. 

Insufficient draft will necessitate additional manipulation of the fuel 
bed and more frequent cleanings to keep its resistance down. Insufficient 
draft also restricts the control by adjustment of the dampers. 

The quantity of excess air present has a marked effect on the draft 
required to produce a given rate of burning, and it is often possible to 
produce a higher rate by increasing the thickness of the fuel bed. 

Combustion of Anthracite 1 

An anthracite fire should never be poked, as this serves to bring ash to 
the surface of the fuel bed where it melts into clinker. 

Egg size is suitable for large firepots (grates 24 in. and over) if the fuel 
can be fired at least 16 in. deep. The air spaces between the pieces of coal 
are large, and for best results this coal should be fired deeply. 



l See reports published by Anthracite Industries Laboratory, Primes, Pennsylvania. 

169 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Stove size coal is the proper size of anthracite for many boilers and 
furnaces used for heating buildings. It burns well on grates at least 16 in. 
in diameter and 12 in. deep. The only instructions needed for burning 
this type of fuel are that the grate should be shaken daily, the fire should 
never be poked or disturbed, and the fuel should be fired deeply and 
uniformly. 

Chestnut size coal is in demand for firepots up to 20 in. in diameter, with 
a depth of from 10 to 15 in. 

Pea size coal is often an economical fuel to burn. It is relatively low 
in price. When fired carefully, pea coal can be burned on standard grates. 
It is well to have a small amount of a larger fuel on hand when building 
new fires, or when filling holes in the fuel bed. Care should be taken to 
shake the grates only until the first bright coals begin to fall through the 
grates. The fuel bed, after a new fire has been built, should be increased 
in thickness by the addition of small charges until it is at least level with 
the sill of the fire door. This keeps a bed of ignited coal in readiness 
against the time when a sudden demand for heat shall be made on the 
heater. A very satisfactory method of firing pea coal consists of drawing 
the red coals toward the front end and piling fresh fuel toward the back 
of the fire-box. 

Pea size coal requires a strong draft and therefore the best results 
generally will be obtained by keeping the choke damper open, the cold- 
air check closed, and by controlling the fire with the air-inlet damper only. 
Pea size can^also be fired in layers with stove or egg size anthracite and 
its use in this manner will reduce the fuel costs and attention required. 
^ Buckwheat size coal for best results requires more attention than pea 
size coal, and in addition the smaller size of the fuel makes it more difficult 
to burn on ordinary grates. Greater care must be taken in shaking the 
grates than with pea coal on account of the danger of the fuel falling 
through the grate. In house heating furnaces the coal should be fired 
lightly and^more frequently than pea coal. When banking a buckwheat 
coal fire it is advisable after coaling to expose a small spot of hot fire by 
putting a poker down through the bed of fresh coal. This will serve to 
ignite ^the gas that will be distilled from the fresh coal and prevent an 
explosion of gas within the firepot, which in some cases depending upon the 
thickness of the bed of fresh coal is severe enough to blow open the doors 
and dampers of the furnace. A good draft is required and consequently 
the fire is best controlled by the air-inlet damper only. Where frequent 
attention can be given and care exercised in manipulation of the grates this 
fuel can be burned satisfactorily without the aid of any special equipment. 
In general it will be found more satisfactory with buckwheat coal to 
maintain a uniform heat output and consequently to keep the system 
warm all the time, rather than to allow the system to cool off at times 
and then to attempt to burn the fuel at a high rate while warming up. A 
uniform low fire will minimize the clinker formation and keep the clinker 
in an easily broken up condition so that it readily can be shaken through 
the grate. 

Forced draft and small mesh grates are frequently used for burning 
buckwheat anthracite. For best results and a higher degree of con- 
venience, domestic stokers are used. 

170 



CHAPTER 9. FUELS AND COMBUSTION 



No. 2 buckwheat anthracite, or rice size, is used only in domestic 
stokers. No. 3 buckwheat anthracite, or barley, has no application in 
domestic heating. 

Firing Bituminous Coal 

Bituminous coal should never be fired over the entire fuel bed at one 
time. A portion of the glowing fuel should always be left exposed to 
ignite the gases leaving the fresh charge. 

Air should be admitted over the fire through a special secondary air 
device, or through a slide in the fire door or by opening the fire door 
slightly. If the quantity of air admitted is too great the gases will be 
cooled below the ignition temperature and will fail to burn. The fireman 
can judge the quantity of air to admit by noting when the air supplied 
is just sufficient to make the gases burn rapidly and smokelessly above the 
fuel bed. 

The red fuel in the firebox, before firing, excepting only a shallow layer 
of coke on the grate, should be pushed to one side or forward or back- 
ward to form a hollow in which to throw the fresh fuel. Some manu- 
facturers recommend that all red fuel be pushed to the rear of the firebox 
and that the fresh fuel be fired directly on the grate and allowed to ignite 
from the top. The object of this is to reduce the early rapid distillation 
of gases and to reduce the quantity of secondary air required for smoke- 
less combustion. 

It is well to have the bright fuel in the firebox so placed that the gases 
from the freshly fired fuel, mixed with the air over the fuel bed, pass 
over the bed of bright fuel on the way to the flues. The bed of bright 
fuel then supplies the heat to raise the mixture of air and gas to the 
ignition temperature, thereby causing the gaseous matter to burn and 
preventing the formation of smoke. 

The fuel bed should be carried as deep as the size of fuel and the 
available draft permit, in order to have as much coked fuel as possible 
for pushing to the rear of the firebox at the time of firing. A deep fuel 
bed allows the longest firing intervals. 

If the coal is of the caking kind the fresh charge will fuse into one 
solid mass which can be broken up with the stoking bar and leveled from 
20 min to one hour after firing, depending on the temperature of the 
firebox. Care should be exercised when stoking not to bring the bar up 
to the surface of the fuel as this will tend to bring ash into the high 
temperature zone at the top of the fire, where it will melt and form 
clinker. The stoking bar should be kept as near the grate as possible 
and should be raised only enough to break up the fuel. With fuels requir- 
ing stoking it may not be necessary to shake the grates, as the ash is 
usually dislodged during stoking. 

The output obtained from any heater with bituminous coal will usually 
exceed that obtainable with anthracite, since soft coal burns more rapidly 
than hard coal and with less draft. Soft coal, however, will require 
frequent attention to the fuel bed, because it burns unevenly, even 
though the fuel bed may be level, forming holes in the fire which admit 
too much air, chilling the gases over the fuel bed and reducing the 
available draft. 

171 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

Semi-bituminous coal is fired as bituminous coal, and because of its 
caking characteristics it requires practically the same attention. The 
Pocahontas Operators Association recommends the central cone method of 
firing, in which the coal is heaped on to the center of the bed forming a 
cone the top of which should be level with the middle of the firing door. 
This allows the larger lumps to fall to the sides, and the fines to remain in 
the center and be coked. The poking should be limited to breaking down 
the coke without stirring, and to gently rocking the grates. It is recom- 
mended that the slides in the firing door be kept closed, as the thinner fuel 
bed around the sides allows enough air to get through. 

Burning Coke 

Coke is a very desirable fuel and usually will give satisfaction as soon 
as the user learns how to control the fire. Coke ignites and burns very 
rapidly with less draft than anthracite coal. In order to control the air 
admitted to the fuel it is very important that all openings or leaks into 
the ashpit be closed tightly. A coke fire responds more rapidly than an 
anthracite fire to the opening of the dampers. This is an advantage in 
warming up the system, but it also makes it necessary to watch the 
dampers more closely in order to prevent the fire from burning too rapidly. 
A deep fuel bed always should be maintained when burning coke. The 
grates should be shaken only slightly in mild weather and should be 
shaken only until the first red particles drop from the grates in cold 
weather. Since coke weighs only about half as much as anthracite per 
cubic foot only about half as much can be put in the firepot, so it will be 
necessary to fire oftener. The best size of coke for general use, for small 
firepots where the fuel depth is not over 20 in., is that which passes over 
a 1 in. screen and through a 1 J^ in. screen. For large firepots where the 
fuel can be fired over 20 in. deep, coke which passes over a 1 in. screen and 
through a 3 in. screen can be used, but a coke of uniform size is always 
more satisfactory. Large sizes of coke should be either mixed with fine 
sizes or broken up before using. 

Dustless Coal 

The practice of treating the more friable coals to allay the dust they 
create is increasing. The coal is sprayed with a solution of calcium 
chloride or a mixture of calcium and magnesium chlorides. Both these 
salts are very hygroscopic and their moisture under normal atmospheric 
conditions keeps the surface of the coal damp, thus reducing the dust 
during delivery and in the cellar, and obviating the necessity of sprinkling 
the coal in the bin. 

The coal is sometimes treated at the mine, but more usually by the 
local distributor just before delivery. The solution is sprayed under high 
pressure, using from 2 to 4 gal or from 5 to 10 Ib of the salt per ton of 
coal, depending on its friability and size. 

Pulverized Coal 

Installations of pulverized coal burning plants in heating boilers are of 
the unit type, in which the pulverized coal is delivered into the furnace 
immediately after grinding, together with the proper amount of preheated 

172 



CHAPTER 9. FUELS AND COMBUSTION 



air. With ^this apparatus, where the necessary furnace volume is ob- 
tainable, high efficiencies can be obtained. 

A 150-hp boiler has generally been considered the smallest size for 
which pulverized fuel is feasible. Complications are introduced if an 
installation with a single boiler has to take care of very light loads. 

Hand Firing 

Hand firing is the oldest and the most widely used method of burning 
coal for heating purposes. To keep the fuel bed in proper condition where 
hand firing is used, the following general rules should be observed: 

1. Remove ash from fuel bed by shaking the grates whenever fresh fuel is fired. This 
removes ash from the fire, enables the air to reach the fuel, and does away with the for- 
mation of clinker which is melted ash. 

2. Supply the boiler with a deep bed of fuel. Nothing is gained by attempting to 
fire a small amount of fuel. A deep bed of fuel secures the most economical results. 

3. Remove ash from ashpit at least once daily. Never allow ash to accumulate up 
to the grates. If the ash prevents the air from passing through, the grate bars will 
burn out and much clinker trouble will be experienced. 

The principal requirements for a hand-fired furnace are that it shall have 
enough grate area and correctly proportioned combustion space. The 
amount of grate area required is dependent upon the desired combustion 
rate. 

The furnace volume is influenced by the kind of coal used. Bituminous 
coals, on account of their long-flaming characteristic, require more space 
in which to burn the gases of combustion completely than do the coals 
low in volatile matter. For burning high volatile coals provision should 
be made for mixing the combustible gases thoroughly so that com- 
bustion is complete before the gases come in contact with the relatively 
cool heating surfaces. An abrupt change in the direction of flow tends to 
mix the gases of combustion more thoroughly. Anthracite requires 
practically no combustion space. 

CLASSIHCATION OF OILS 

Uniform oil specifications were prepared in 1929 by the American Oil 
Burner Association, in cooperation with the American Petroleum Institute, 
the U. S. Bureau of Standards, the American Society for Testing Materials 
and other interested organizations. Oil fuels were classified into six 
groups, as indicated by Table 3. When these specifications were prepared, 
it was generally accepted that the first three grades were adapted to 
domestic use, while the last three were suitable only for commercial and 
industrial burners. 

^ Today domestic -installations may use No. 4 oil of the so-called heavy 
oil group, when and if said oil very closely follows the specifications of 
No. 3. Up-to-date listing by the Underwriter's Laboratories should be 
referred to before a No. 4 grade of fuel is used which merely meets 
Commercial Standards CS 12-35. 

Since the specifications as originally drawn provide for maximum limits 
only for the several grades, this differentiation has not proved stable. 
Realizing how unsatisfactory it is to have specifications which permit the 

173 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 3. COMMERCIAL STANDARD FUEL OIL SPECIFICATIONS* 
A. Detailed Requirements for Domestic Fuel Oils* 



GRADE OF OIL 


APPROX. 
Bxu 

PER 

GAL." 


FLASH POINT 


WATER 

AND 

SEDIMENT, 
MAXIMUM 


CARBON 

RESIDUE 
MAXIMUM 


DISTILLATION 
TEST 


VISCOSITY 
MAXIMUM 


Min. Max. 


Max. 1 Min. 


No. 1 
Domestic 
Fuel Oil 
A light distillate 
oil for use in 
burners requir- 
ing a high grade 
fuel. 


139,000 


100 F 150 F 
or legal 


0.05% 


0.02% 


10% point 
420 F 

End point 
600 F 






No. 2 
Domestic 
Fuel Oil 
A medium distil- 
late oil for use 
in burners re- 
quiring a high 
grade fuel. 


141,000 


125 F 190 F 
or legal 


0.05% 


0.05% 


10% point 

90% point 
620 F 


End point 
600 F 




No. 3 
Domestic 
Fuel Oil 
A distillate fuel 
oil for use in 
burners where a 
low viscosity oil 
is required. 


143400 


150 F i 200 F 
or legal' 


0.1% 


0.15% 




90% point 
620 F 


Saybolt 
Universal 
at 100 F 
70 seconds 


Adapted from "Fuel Oils," p. 2, U. S, Department of Commerce, Bureau of Standards, Commercial 
Standard CS18-S5, Washington, 1935. 



&POUT Point Maximum is 15 F. Lower or higher pour points may be specified whenever required by 
conditions of storage and use. However, these specifications shall not require a pour point less than F 
under any conditions. 

"Government specifications do not give Btu per gallon, but they are noted here for information only. 



B. Detailed Requirements for Industrial Fuel Oils* 



GRADE OF On. 


APPROX. 
BTU 

PER 

GAL. 


FLASH POINT, 


WATER 

AND 

SEDIMENT, 
MAXIMUM 


ASH 
MAXIMUM 


VISCOSITY, 

MAXIMUM 


Min. 


Max. 


No. 4. 
Industrial Fuel Oil 

An oil known to the trade as a light fuel 
oil for use in burners where a low vis- 
cosity industrial fuel oil is required. 


144,500 


150 F 


See 

Note* 


1-0% 


0.1% 


Saybolt 
Universal 
at 100 F 
500 seconds 


No. 5 

Industrial Fuel Oil 

Same as Federal Specifications Board 
specification for bunker oil "B" for 
burners adapted to the use of indus- 
trial fuel oil of medium viscosity. 


146,000 


150 F 




1.0% 


0.15% 


Saybolt 
Furol 
at 122 F 
100 seconds 


No. 6 
Industrial Fuel Oil 

Same as Federal Specifications Board 
specification for bunker oil "C" for 
burners adapted to oil of high viscosity 


150,000 


150 F 




2.0% 




Saybolt 
Furol 
at 122 F 
300 seconds 



*Pour point may be specified whenever required by conditions of storage and use. However, these 
specifications shall not require a pour point less than 15 F under any conditions. 

Whenever required, as for example in burners with automatic ignition, a maximum flash point may 
be specified. However, these specifications shall not require a flash point less than 250 F under any con- 
ditions. 

174 



CHAPTER 9. FUELS AND COMBUSTION 



substitution of one grade for another, the U. 5. Bureau of Standards in 
cooperation with the American Society for Testing Materials is figuring 
on a new set of specifications providing for definite limits for each grade. 
When these specifications are adopted, it is expected that the National 
Board of Fire Underwriters will retest all burners using oils of the maximum 
specifications for the grade so that if a burner is approved for a certain 
grade it will burn any oil meeting the specifications for that particular 
grade. 

Several burners adapted to industrial use have recently been listed for 
automatic operation with No. 5 oil. Usually oils No. 5 or 6 require 
preheating for proper operation, but where conditions are favorable, No. 
5 can be used without the equipment that this entails. 

There are two reasons for the trend to lower grades of oil. While the 
lighter ^oils contain slightly more heat units per pound, the weight per 
gallon increases more rapidly than the decrease in heat units per pound, 
and oil is bought by the gallon. As a consequence, while a No. 1 oil may 
contain 139,000 Btu per gallon, oil No. 5 may test 146,000 Btu per gallon, 
or 6 per cent more. Usually there is a differential of 3 to 4 cents between 
the No. 1 and No. 5 oils, so that the economy of buying the heavier fuels 
is apparent; there remains the economic utilization of the heat content of 
the heavier oils. 

The cost of oil fuel is dependent also upon the amount that can be 
delivered at one time, and the method of delivery. Common practice has 
split the tank of the truck delivering oils for domestic use into compart- 
ments of 150 to 500-gal capacity, and these unit dumps are made the basis 
of price. Where a truck can be connected to a storage-tank fill and 
quickly discharge its oil by pump, the price obviously can be less than 
where a smaller quantity must be drawn off in 5-gal cans and poured. 
For similar reasons an installation that can be supplied from a tank car 
on a siding provides for a lower unit fuel cost than one where the oil 
must be trucked, even in the large trucks holding 2,000 gal or more that 
are used for distributing the heavier oils. 

GAS CLASSIFICATION 

Gas is broadly classified as being either natural or manufactured. 
Natural gas is a mechanical mixture of several combustible and inert 
gases rather than a chemical compound. Manufactured gas as dis- 
tributed is usually a combination of certain proportions of gases produced 
by two or more processes, and is often designated as city gas. 

When gas is burned a large amount of water vapor is produced as one 
of the products of combustion. This ordinarily escapes up the chimney, 
carrying away with it a certain amount of heat. However, when the heat 
value of gas is determined in an ordinary calorimeter, this water vapor 
is condensed and the latent heat of vaporization that is given up during 
the condensation is reported as a portion of the heat value of the gas. 
The heat value so determined is termed the gross or higher heat value and 
this is what is ordinarily meant when the heat value of gas is specified. 
The heat that is reclaimed by the condensation of the water vapor 
amounts to about 10 per cent of the total heat value. It is impractical 
to utilize the entire higher heat value of the gas in any house-heating 

175 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



appliance, because to do so it would be necessary to cool the products of 
combustion down below their dew point, which is ordinarily in the 
neighborhood of 130 F. 

The actual dew point in the chimney is different from the theoretical 
value because excess air is admitted not only at the burner but also at the 
backdraft diverter which lowers the dew point. 

Natural gas is the richest of the gases and contains from 80 to 95 
per cent methane, with small percentages of the other combustible 
hydrocarbons. In addition, it contains from 0.5 to 5.0 per cent of CO*, 
and from 1 to 12 or 14 per cent of nitrogen. The heat value varies from 
700 to 1500 Btu per cubic foot, the majority of natural gases averaging 
about 1000 Btu per cubic foot. Table 4 shows typical values for the 
four main oil fields, although values from any one field vary materially. 

Table 4 also gives the calorific values of the more common types of 
manufactured gas. Most states have legislation which controls the distri- 
bution of gas and fixes a minimum limit to its heat content. The gross 
or higher calorific value usually ranges between 520 and 545 Btu per cubic 
foot, with an average of 535. A given heat value may be maintained and 
yet leave considerable latitude in the composition of the gas so that as 
distributed the composition is not necessarily the same in different dis- 

TABLE 4. REPRESENTATIVE PROPERTIES OF GASEOUS FUELS, 
BASED ON GAS AT 60 F AND 30 IN. HG. 



GAS 


BnjMBCuFr 


SPECIFIC 
GBATHT, 
Am - 
1.00 


Ant RxQtnBXD 
FOE COMBUS- 
TION, 
(CuFr) 


PRODUCTS or COMBUSTION 


THEOBBTZCAL 
FLAME TEM- 

PEBATUHB, 

(DEO FAHB) 


TTigh 

(Gross) 


Low 
(Net) 


Cubic Feet 


ULTI- 
MATE 

GO* 

Dry 
Basis 


COt 


H0 


Total 
with 

N* 


Natural gas 
California 


1200 


1087 


0.67 


11.26 


1.24 


2.24 


12.4 


12.2 


3610 


Natural gas 
Mid-Conti- 
nental 


967 


873 


0.57 


9.17 


0.97 


1.92 


10.2 


11.7 


3580 


Natural gas 
Ohio 


1130 


1025 


0.65 


10.70 


1.17 


2.16 


11.8 


12.1 


3600 


Natural gas 
Pennsylvania 


1232 


1120 


0.71 


11.70 


1.30 


2.29 


12.9 


12.3 


3620 


Retort coal gas 


575 


510 


0.42 


5.00 


0.50 


1.21 


5.7 


11.2 


3665 


Coke oven gas 


588 


521 


0.42 


5.19 


0.51 


1.25 


5.9 


11.0 


3660 


Carburetted 
water gas 


536 


496 


0.65 


4.37 


0.74 


0.75 


5.0 


17.2 


3815 


Blue water gas 


308 


281 


0.53 


2.26 


0.46 


0.51 


2.8 


22.3 


3800 


Anthracite pro- 
ducer gas 


134 


124 


0.85 


1.05 


0.33 


0.19 


1.9 


19.0 


3000 


Bituminous 
producer gas 


150 


140 


0.86 


1.24 


0.35 


0.19 


2.0 


19.0 


3160 


Oil gas 


575 


510 


0.35 


4.91 


0.47 


1.21 


5.6 


10.7 


3725 



176 



CHAPTER 9. FUELS AND COMBUSTION 



tricts, nor at successive times in the same district. There are limits to the 
variation allowable, because the specific gravity of the gas depends on its 
composition, and too great a change in the specific gravity necessitates a 
change in the adjustment of the burners of small appliances. 

Table 4 shows that a large proportion of the products of combustion 
when gas is burned may consist of water vapor, and that the greater the 
proportion of water vapor, the lower the maximum attainable C0$ by gas 
analysis. The table also shows that a low calorific value does not neces- 
sarily mean a low flame temperature since, for example, natural gas has a 
theoretical flame temperature of 3600 F and blue water gas of 3800 F, 
although it has a calorific value less than one third that of natural gas. 

The quantity of air given in Table 4 is that required for theoretical 
combustion, but with a properly designed and installed burner the excess 
air can be kept low. The division of the air into primary and secondary 
is a matter of burner design and the pressure of gas available, and also of 
the type of flame desired. 

PROBLEMS IN PRACTICE 

1 Differentiate between the general characteristics of hard and soft coals* 

Hard coals contain fixed carbon in large proportions and in addition more ash is present 
especially in the smaller sizes. Soft coals have an increasing percentage of carbon in 
combination with hydrogen which is volatile and will distill off under high temperature, 
producing smoke. 

2 Name several important properties of coal from a utilization standpoint. 

a. Caking tendency, whether none, weak, or strong. 

b. Quantity of volatile matter. 

c. Friability. 

d. Fusibility of the ash. 

3 What are the main data commonly available that fix the qualities of coal, 
and do these tell the whole story? 

a. Calorific value, Btu per pound. 

b. Proximate analysis giving percentages of moisture, volatile matter, fixed carbon, ash, 
and sulphur. 

c. Temperature at which the ash softens. 

d. Screen sizes. 

Other important qualities not usually given are the friability of the coal, its caking 
tendency, and the qualities of the volatile matter. The percentage of ash and its fusion 
temperature do not tell how the ash is distributed or how much of it is less fusible lumps 
of slate or shale. 

4 Are there available complete and sufficient data on gas and oils to fix their 
burning properties and furnace requirements? 

Yes. Because gas and oils are of simple and uniform composition, data are available to 
fix their burning properties and furnace requirements, but the ability to control their 
combustion is somewhat less determinable. 

5 What effect does moisture in fuels have on their efficiency? 

With any solid fuel, latent and sensible heat are lost at the stack when moisture is dried 
out of the fuel in burning, and when its hydrogen is burned. Therefore, such fuels as 
sub-bituminous coal and lignite, which are high in moisture content, have a low efficiency. 
However, these efficiencies may be improved if the stack gases are cooled to room tem- 
perature, by heating the feed water, for example. 

177 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

6 What are the advantages of a sized fuel for heating furnaces? 

Because a sized fuel encourages a more uniform flow of air through the bed, the burning 
will be more uniform, and the bed will be less liable to develop holes and will require less 
attention. Uniformity of fuel size is more desirable as the area of the bed becomes 
smaller; it is less important with fuels that cake, but with sized fuels the caking will be 
more uniform and the air flow through the bed will be steadier. In addition, ash and 
pieces of slate are less likely to be segregated and to form lumps of clinker. 

7 Does the size of a fuel affect the quantity of air required to burn it at a 
given rate? 

The total air required to give the same gas analysis at the stack^is independent of the 
size of the fuel burned, but for non-caking fuels the ratio of the air passing through the 
fuel bed to the total air entering the burner base decreases, for the same^thickness of bed, 
as the size of the fuel becomes smaller; this decrease is very rapid for sizes less than one 
inch. For coals that cake, this ratio will depend on the way the caked bed is broken up 
and on the size of the resulting pieces. 

8 Is the volatile matter which is given off when coals are burned of the same 
nature in all coals? 

No. The products given off by coals when they are heated differ materially in the ratios 
by weight of the gases to the oils and tars. No heavy oils or tars are given off by anthra- 
cite, and very small quantities are given off by semi-anthracite. As the volatile matter 
in the coal increases to as much as 40 per cent of ash-free and moisture-free coal, in- 
creasing amounts of oils and tars are given up. For coals of higher volatile content, the 
relative quantity of oils and tars decreases, so it is low in the sub-bituminous coals and 
in lignite. 

9 Is smoke a primary product hi the burning of fuels? 

Visible smoke may include very small particles of carbon, oil, tar, water (condensed 
steam), and ash. Of these, the oils, tars, and ash are mainly primary products, and the 
water is partly primary. The carbon, which usually comprises the greater part of the 
smoke, results from the breaking up by heat of oils, tars, and such gases as methane, so 
it may be considered a secondary product. 

10 Is the sulphur in coals detrimental to combustion? 

Not so far as is known, but its complete combustion gives only 25 per cent as much heat 
as is given by the same weight of carbon. Sulphur is undesirable because it causes cor- 
rosion of flues and stacks, and also because its gases pollute the atmosphere, and damage 
buildings and vegetation. 

11 How do deposits of soot on the surfaces of a boiler or heater affect the 
quantity of fuel burned? 

There are two effects. The scot acts as an insulating layer over the surface and reduces 
the heat transmission to the water or air; the Bureau of Mines Report of Investigations 
No. 3272 shows that the loss of seasonal efficiency is not as great as has been believed and 
should not be over 6 per cent because the greater part of the heat is transmitted through 
the firepot. The soot clogs the passages and reduces the draft; the loss of efficiency 
from this action may be much more, and also the lack of draft results in unsatisfactory 
heating. 



178 



Chapter 10 

CHIMNEYS AND DRAFT CALCULATIONS 

Natural Draft, Mechanical Draft, Characteristics of Natural 
Draft Chimneys, Determining Chimney Sizes, General Equa- 
tion, Chimney Construction, Chimneys for Gas Heating 

THE design and construction of a chimney is so important a part 
of the heating engineer's work that a general knowledge of draft 
characterictics and calculations is essential. 

Draft, in general, may be defined as the pressure difference between the 
atmospheric pressure and that at any part of an installation through 
which the gases flow. Since a pressure difference implies a head, draft 
is a static force. While no element of motion is inferred, yet motion 
in the form of circulation of gases throughout an entire boiler plant 
installation is the direct result of draft. This motion is due to the pressure 
difference, or unbalanced pressure, which compels the gases to flow. Draft 
is often classified into two kinds according to whether it is created 
thermally or artificially, viz, (1) natural or thermal draft, and (2) arti- 
ficial or mechanical draft. 

Natural Draft 

Natural draft is the difference in pressure produced by the difference in 
weight between the relatively hot gases inside a natural draft chimney and 
an equivalent column of the cooler outside air, or atmosphere. Natural 
draft, in other words, is an unbalanced pressure produced thermally by a 
natural draft chimney as the pressure transformer and a temperature 
difference. The intensity of natural draft depends, for the most part, 
upon the height of the chimney above the grate bar level and also the 
temperature difference between the chimney gases and the atmosphere. 

A typical natural draft system consists essentially of a relatively tall 
chimney built of steel, brick, or reinforced concrete, operating with the 
relatively hot gases which have passed through the boilers and accessories 
and from which all the heat has not been extracted. Hot gases are an 
essential element in the operation of a natural draft system, although 
inherently a heat balance loss. 

A natural draft chimney performs the two-fold service of assisting in 
the creation of draft by aspiration and also of discharging the gases at an 
elevation sufficient to prevent them from becoming a nuisance. 

Natural draft is quite advantageous in installations where the total loss 
of draft due to resistances is relatively low and also in plants which have 
practically a constant load and whose boilers are seldom operated above 

179 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



their normal rating. Natural draft systems have been, and are still being, 
employed in the operation of large plants during the periods when the 
boilers are operated only up to their normal rating. When the rate of 
operation is increased above the normal rating, some form of mechanical 
draft is employed as an auxiliary to overcome the increased resistances or 
draft losses. Natural draft systems are used almost exclusively in the 
smaller size plants where the amount of gases generated is relatively small 
and it would be expensive to install and operate a mechanical draft 
system. 

The principal advantages of natural draft systems may be summarized 
as follows: (1) simplicity, (2) reliability, (3) freedom from mechanical 




FIG. 1. GENERAL OPERATING CHARACTERISTICS OF TYPICAL INDUCED DRAFT FAN 

parts, (4) low cost of maintenance, (5) relatively long life, (6) relatively 
low depreciation, and (7) no power required to operate. The principal 
disadvantages are: (1) lack of flexibility, (2) irregularity, (3) affected 
by surroundings, and (4) affected by temperature changes. 

Mechanical Draft 

^Artificial draft, or mechanical draft, as it is more commonly called, is a 
difference in pressure produced either directly or indirectly by a forced 
draft fan, an induced draft fan, or a Venturi chimney as the pressure 
transformer. The intensity of mechanical draft is dependent for the most 
part upon the size of the fan and the speed at which it is operated. The 
element of temperature does not enter into the creation of mechanical 
draft and therefore its intensity, unlike natural draft, is independent of the 
temperature of the gases and the atmosphere. Mechanical draft includes 
the induced and Venturi types of draft systems in which the pressure 
difference is the result of a suction, and also the forced draft system in 
which the pressure difference is the result of a blowing. Mechanical draft 
systems^tend to produce a vacuum or a plenum, as the system used in its 
production creates a pressure difference below, or above, atmospheric 

1RO 



CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS 































1 






















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410 
















X 1 








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5jn 


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*S' 


A 






















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4OO 












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fl. 


380 
























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45 


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50 





V* 





C 


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to 





FIG. 2. OPERATING CHARACTERISTICS OF TYPICAL CENTRIFUGAL PUMP 

pressure, respectively. A mechanical draft system may be used either in 
conjunction with, or as an adjunct to, a natural draft system. 

Draft Control 

To obtain the maximum efficiency of combustion, a definite minimum 
supply of air to the combustion chamber must be maintained. To pro- 
vide this condition, it is necessary to have some mechanical means of 
draft control or adjustment, because of variable wind velocities, fluctua- 
tions in atmospheric temperatures and barometric pressures, and their 
effect upon draft. 

For this purpose there are various mechanical devices which auto- 
matically control the volume of air admitted to the combustion chamber. 
Mechanical draft regulators designed to control or adjust draft, should 



1.4 
1.2 
1.1 

S 

|0.8 

307 

*0.6 

005 
. 
0.4 
03 
0.2 
0.1 

c 








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ps 






































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=x 


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ff> c 


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A 


) 30 60 90 120 150 180 210 240 270 30( 
Amount of Gases Flowing and Discharged, H>. per sea, W 



FIG. 3. TYPICAL SET OF OPERATING CHARACTERISTICS OF A NATURAL DRAFT CHIMNEY 

181 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

not be confused with mechanical draft systems that create draft mechani- 
cally, but which must also be automatically controlled. 

The use of such a device to provide a more uniform and dependable 
control of draft than could be maintained by manually operated dampers, 
will produce better combustion of fuel. This higher efficiency of combus- 
tion together with the reduced heat losses up the chimney by reason of 
decreased gas velocity, results in fuel economy, with consequent lower 
costs of plant operation. 

CHARACTERISTICS OF CHIMNEYS 

In order to analyze the performance of a natural draft chimney, it may 
be advantageous to compare its general operating characteristics with 
those of a centrifugal pump and also of a centrifugally-induced draft fan, 
there being a similarity among the three. Figs. 1, 2 and 3 show the 
general operating characteristics of a typical centrifugally-induced draft 
fan, a typical centrifugal pump, and a typical natural draft chimney, 
respectively. The draft-capacity curve of the chimney corresponds to 
the head-capacity curve of the pump and also to the dynamic-head 
capacity curve of the fan. 

When the gases in the chimney are stationary, the draft created is 
termed the theoretical draft. When the gases are flowing, the theoretical 
intensity is diminished by the draft loss due to friction, the difference 
between the two being termed the total available draft. The general 
equation for this net total available draft intensity of a natural draft 
chimney with a circular section is as follows: 

D -2Qfim? ( W * W *\ 0-00126 W7V/ m 

P a - 2.9ftOT (jr-jr) ^^ (D 

where 

D & = available draft, inches of water. 
H height of chimney above grate bars, feet. 

BQ ~ barometric pressure corresponding to altitude, inches of mercury. 
W = unit weight of a cubic foot of air at F and sea level atmospheric pressure, 

pounds per cubic foot. 
W c unit weight of a cubic foot of chimney gases at F and sea level atmospheric 

pressure, pounds per cubic foot. 

To absolute temperature of atmosphere, degrees Fahrenheit. 
TC = absolute temperature of chimney gases, degrees Fahrenheit. 
W amount of gases generated in the combustion chamber of the boiler and passing 

through the chimney, pounds per second. 
/ ~ coefficient of friction. 

L = length of friction duct of the chimney, feet. 
D = minimum diameter of chimney, feet. 

The first term of the right hand expression of Equation 1 represents 
the theoretical draft intensity, and the second term, the loss due to friction. 

Example 1. _ Determine the available draft of a natural draft chimney 200 ft in height 
and 10 ft in diameter operating under the following conditions: atmospheric tempera- 
ture, 62 F; chimney gas temperature, 500 F; sea level "atmospheric pressure, B = 29.92 
in. of mercury; atmospheric and chimney gas density, 0.0863 and 0.09, respectively; 
coefficient of friction, 0.016; length of friction duct, 200 ft. The chimney discharges 
100 Ib of gases per second. 

182 



CHAPTER 10. CHIMNEYS AND DRAFT CALCUUITIONS 



Substituting these values in Equation 1 and reducing: 



2.96 X 200 X 29.92 X 



0863 Q.09\ 0.00126 X 100* X 960 X 0.016 X 200 



/0.086S 
\ 522 



960 / 



10* X 29.92 X 0.09 



1.27 - 0.14 ~ 1.13 in. 



Fig. 3 shows the variation in the available draft of a typical 200 ft by 
10 ft chimney operating under the general conditions noted in Example 1. 
When the chimney is under static conditions and no gases are flowing, the 
available draft is equal to 1.27 in. of water, the theoretical intensity. As 
the amount of gases flowing increases, the available intensity decreases 
until it becomes zero at a gas flow of 297 Ib per second, at which point the 
draft loss due to friction is equal to the theoretical intensity. The draft- 
capacity curve corresponds to the head-capacity curve of centrifugal 



ou 
29 

28 
5 
.27 

26 

25 
24 
| 23 
m 22 

21 
20 


X 


'V,. 






























\ 
































\ 


s 






























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,. 






























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^ 






























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s^ 






























s>v 


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) 1000 2000 3000 4000 5000 6000 70C 
Corresponding Altitude above Sea Level, ft 



FIG. 4. RELATION BETWEEN BAROMETRIC PRESSURE AND ALTITUDE 

pump characteristics and the dynamic-head-capacity curve of a fan. The 
point of maximum draft and zero capacity is called shut-off draft, or point 
of impending delivery, and corresponds to the point of shut-off head of a 
centrifugal pump. The point of zero draft and maximum capacity is 
called the wide open point and corresponds to the wide open point of a 
centrifugal pump. A set of operating characteristics may be developed 
for any size chimney operating under any set of conditions by substituting 
the proper values in Equation 1 and then plotting the results in the 
manner shown in Fig. 3. 

In substituting the values for the various factors in Equation 1, care 
should be exercised that the selections be as near the actual conditions as 
is practically possible. The following notes will serve as a guide for these 
selections: 

1. The barometric pressure varies inversely as the altitude of the plant above sea level 
Fig. 4 gives the barometric pressure corresponding to various elevations as computec 
from the equation : 



where 



En - 62,737 logi 

= altitude of plant above sea level, feet. 

183 



(2 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

In general, the barometric pressure decreases approximately 0.1 in. of mercury per 100 
ft increase in elevation. 

2. The unit weight of a cubic foot of chimney gases at F and sea level barometric 
pressure is given by the equation: 

W c 0.131 CO, -f 0.095 02 -f 0.083 N t (3) 

In this equation CO^ O* and Nt represent the percentages of the parts by volume of the 
carbon dioxide, oxygen and nitrogen content, respectively, of the gas analysis. For 
ordinary operating conditions, the value of W c may be assumed at 0.09. 

The density effect on the chimney gases due to superheated water vapor resulting 
from moisture and hydrogen in the fuel, or due to any air infiltrations in the chimney 
proper are here disregarded. Though water vapor content is not disclosed by Orsat 
analysis, its presence tends to reduce the actual weight per cubic foot of chimney gases. 

3. The atmospheric temperature is the actual observed temperature of the outside air 
at the time the analysis of the operating chimney is made. The mean atmospheric 
temperature in the temperate zone is approximately 62 F. 

4. The chimney gas^ temperature does not vary appreciably from the gas temperature 
as it leaves the breeching and enters the chimney. For average operating conditions, the 
chimney gas temperature will vary between 500 F and 650 F except in the case when 
economizers and recuperators are used, when the temperature will vary between 300 F 
and 450 F. If a chimney has been properly constructed, properly lined and has no air 
infiltration due to open joints, the temperature of the gases throughout the chimney will 
not differ appreciably from the foregoing figures. In most up-to-date heating plants, the 
temperature may be read from instruments or ascertained from a pyrometer. The 
analysis of this section is predicated on the assumption of constant gas temperature and 
no air infiltration throughout the height of the chimney. 

5. The coefficient of friction between the chimney gases and a sooted surface has been 
taken by many workers in this field as a constant value of 0.016 for the conditions in- 
volved. This value, of course, would be less for a new unlined steel stack than for a 
brick or brick-lined chimney, but in time the inside surface of all chimneys regardless of 
the materials of construction becomes covered with a layer of soot, and thus the coef- 
ficient of friction has been taken the same for all types of chimneys and in general 
constant for all conditions of operation. For reasons of simplicity and convenience to 
the^reader, this constant value of 0.016 has been employed in the development of the 
various special equations and charts shown in this chapter. 

However, much to be recommended as an alternate method is the practise of separ- 
ately determining duct friction factors as a function of the flow conditions, specifically 
as a function of the Reynolds number and the relative duct roughness. The Reynolds 
criterion is based on the physical properties of the gas, the duct dimensions, and the gas 
velocity. The gas velocity for a chimney is usually well above the critical velocity. 
It is likely that this procedure of using a separately determined variable friction factor 
for chimney flow will give results that are to be preferred over those based on a set 
constant. 

The Reynolds number, a dimensionless ratio, may be stated as follows: 

. C r =^ (4) 

where 

D = chimney diameter, feet. 
V - velocity of hot gas, feet per second, 
p = mass density of the chimney gas per cubic foot. 

(i = viscosity of the gas in pounds-second per square foot taken at the gas tem- 
perature. 

In another form: 

1.27 W 0.039617 



184 



CHAPTER 10. CHIMNEYS AND DRAFT CALCUIATIONS 



where 



weight of gas passed per second. 
acceleration of gravity. 



The value of jj, for chimney gases is usually taken as that of air or nitrogen, and for the 
variation of p, with temperature, the Sutherland equation may be employed as follows, 
giving n in pounds-second per square foot: 

f273 + C\ f T c 

^ " ^ Lr c + cj L273 
where 

T c chimney gas temperature, degrees Centigrade. 
pLo = gas viscosity at C. 
C constant for specific gas. 



Using International Critical Table values, for air 
nitrogen IK> = 34.5 X 10-8; and C = 110. 



35.6 X 10-8; C = 12-4; for 



0.010 




0.001 



40 60 80 100 200 

REYNOLDS NUMBER, IN THOUSANDS 



FIG. 5. VARIATION OF FRICTION FACTOR / WITH REYNOLDS NUMBER 

Values for the viscosity of air and of nitrogen (the principal component of chimney 
gases) for the different temperatures follow, in which the values given in pounds-second 
per square foot are to be multiplied by 10-8: 



Temp. F 

Air 

Nitrogen 



300 

49.7 

47.7 



400 

54.5 

52.2 



500 

58.5 

56.0 



600 

62.5 

59.8 



700 

66.7 

63.5 



800 

70.5 

67.0 



Example 2. To determine the Reynolds number C r for a flow of 118 Ib gas per second 
up a 12 ft diameter chimney at a temperature of 500 F. The gas may be assumed to 
have the same viscosity as nitrogen at 500 F. Using Equation 5 : 



n AO 
= 0.0396 = 



- 0396 X 118 



12 



x 



The variation of the friction factor/ with the Reynolds number is shown in Fig. 5 1 . 
Three curves are shown: A, B, and C, where the choice of the friction factor curve 
depends on the relative surface roughness, and this for usual chimney construction may 



iSee also Flow of Fluids in Closed Circuits, by R. J. S. Pigott (Mechanical Engineering, August, 1933). 

185 



HEATING VENTIIATINO AIR CONDITIONING GUIDE 1938 



be selected by size since surface conditions in service are always undetermmant. For 
sizes up to 3 ft in diameter, Curve C may be used; from 3 to 6 ft, Curve B ; and from 6 ft 
upwards, Curve A. Thus for the previous example with CT = 698,000 and 12 ft diameter, 
/ would be taken from Curve A as 0.0039. 

6. The length of the friction duct is the vertical distance between the bottom of the 
breeching opening and the top of the chimney. Ordinarily this distance is approximately 
equal to the height of the chimney above the grate level. 




.001 .002 .003 .004 .005 .006 
Available Draft per Ft of Height, in. of Water 



.007 



FIG. 6. CHIMNEY PERFORMANCE CHART* 

*ro scive a typical example: Proceed horizontally from a Weight Flow Rate point to intersection with 
diameter line; from this intersection follow vertically to chimney height line; from this intersection follow 
horizontally to the right to Available Draft scale. Starting from a point of Available Draft, take steps in 
reverse order. 



7. Assuming no air infiltration the amount of gases flowing and being discharged is, 
of course, equal to the amount of gases generated in the combustion chamber of the 
boiler. The total products of combustion in pounds per second for a grate-fired boiler 
may be computed from the equation: 



W - 



where 



3600 



(6) 



C & = pounds of fuel burned per square foot of grate surface per hour. 
G ~ total grate surface of boilers, square feet. 
C g X G = total weight of fuel burned per hour. 

Wtp = total weight of products of combustion per pound of fuel. 

A similar computation may be made in the case of gas, oil, or stoker-fired fuel. 

186 



CHAPTER 10. CHIMNEYS AND DRAFT CALCUIATIONS 

Fig ; 6 Is a typical chimney performance chart giving the available draft 
intensities for various amounts of gases flowing and sizes of chimney. 
This chart is based on an atmospheric temperature of 62 F, a chimney gas 
temperature of 500 F, a unit chimney gas weight of 0.09 Ib per cubic foot, 
sea level atmospheric pressure, a coefficient of friction of 0.016, and a 
friction duct length equal to the height of the chimney above the grate 
level. These curves may be used for general operating conditions. For 
specific operating conditions, a new chart should be constructed from 
Equation 1. 

It has been the usual custom, and still is to a lamentably great extent, 
to select the required size of a natural draft chimney from a table of 
chimney sizes based only on boiler horsepowers. After the ultimate 
horsepower of the projected plant had been determined, the chimney size 
in the table corresponding to this figure was then selected as the proper 
size required. Generally, no further attempt was made to determine if 
the height thus selected was sufficient to help create the required draft 
demanded by the entire installation, or the diameter sufficiently large to 
enable the chimney quickly, efficiently, and economically to dispose of the 
gases. Since the operating characteristics of a natural draft chimney are 
similar in all respects to those of a centrifugal pump, or a centrifugal fan, 
it is no more possible to select a proper size chimney from such a table, 
even with correction factors appended, than it is to select the proper size 
pump from tables based only on the amount of water to be delivered. 

DETERMINING CHIMNEY SIZES 

The required diameter and height of a natural draft chimney are given 
by the following equations: 



V* (7) 

D - 0.288 J WTc (8) 

* B W C V 

where 

H = required height of chimney above grate bar level, feet. 
D = required minimum diameter of chimney, feet (constant for entire height), 
V = chimney gas velocity, feet per second. 

p r = total required draft demanded by the entire installation outside of the chimney, 
inches of water. 

Equations 7 and 8 give the required size of a natural draft chimney with 
all of the operating factors taken into consideration. Values for all of the 
factors with the exception of the chimney gas velocity may be either 
observed or computed. It is, of course, necessary to assume an arbitrary 
value for the velocity in order to arrive at some definite size. For any one 
set of operating conditions tjiere will be as many sizes of chimneys as there 
are values of reasonable velocities to assume. Of the number of sizes 
corresponding to the various assumed velocities, there is one size which 
will be least expensive. Since the cost of a chimney structure, regardless 

187 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

of the kind of material used in the construction, varies as the volume of 
material in the structure, the cost criterion then may be represented by 
the approximate equation : 

Q = ttHD (9) 

where 

Q - volume of material, cubic feet. 
t average wall thickness, feet. 

For all practical purposes, the value of xt may be taken as a constant 
regardless of the size of the structure. Hence, in general, the volume, and 
consequently the cost, of a chimney structure may be based on the factor 
HD as a criterion. Therefore, the value of the chimney gas velocity which 
will result in the least value of HD for any one set of operating con- 
ditions will produce a structure which will be the most economical to use, 
because its cost will be least. 

The problem at hand is to deduce an equation for the chimney gas 
velocity which will result in a combination of a height and a diameter 
whose product HD will be least. The solution is obtained by equating the 
product of Equations 7 and 8 to HD, differentiating this product with 
respect to V and equating the resulting expression to zero. This pro- 
cedure results in the following expression : 



772r Q c 2/5 

_ TO " 

" \ 
where F c economical chimney gas velocity, feet per second. 

Equation 10 gives the economical velocity of the chimney gases for 
any set of operating conditions, and represents the velocity which will 
result in a chimney the size of which will cost less than that of any other 
size as determined by any other velocity for the same operating con- 
ditions. After the value of the economical velocity has been determined, 
the corresponding height and diameter can then be determined from 
Equations 7 and 8, respectively, and the economical size will then be 
attained. Equations 7, 8 and 10 may be simplified considerably for 
average operating conditions in an average size steam plant by assuming 
typical conditions. 

Average chimney gas temperature, 500 F ....... __________________ T c = 960 

Mean atmospheric temperature, 62 F _____ ......................... T Q = 522 

Average coefficient of friction, 0.016 ____________________________________ ./ 0.016 

Average chimney gas density, 0.09. ________________________________ W c = 0.09 

Sea level elevation, with barometer of 29.92 _____ ............... B - 29.92 

Substituting these values in Equations 10, 8 and 7, respectively, and 
reducing, the results are substantially: 



- (11) 

D - 1.5T7 2 / 5 (12) 

H = 1901>r (13) 
188 



CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS 



Fig. 7 gives the economical chimney sizes for various amounts of gases 
flowing and for required draft intensities as computed from Equations 11, 
12 and 13. They are based on the operating factors used in reducing 
Equations 7, 8 and 10 to their simpler form. The sizes shown by the 
curves in the chart should be used for general operating conditions only, 
or for installations where the required data necessary for an exact deter- 



Height of Chimney, ft. 
^0 25 50 75 100 125 150 1 75 200 225 250 275 300 325 350 371 




01234 



5 6 7 8 9 10 11 12 
Diameter of Chimney, ft 



13 14 15 



FIG. 7. ECONOMICAL CHIMNEY SizEs a 

aDiameter values also for gas temperatures of 400, 500 and 600 F 



mination are difficult or impossible to secure. Whenever it is possible to 
secure accurate data, or the anticipated operating conditions are fairly 
well known, the required size should be determined from Equations 7, 
8 and 10. The recommended minimum inside dimensions and heights of 
chimneys for small and medium size installations are given in Table 1. 



GENERAL EQUATION 

The general draft equation for a steam producing plant may be stated 
as follows: 

0t - Af - *F + AB -h ted + feC + feBr + &V + ho + &B + &R (14) 

189 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

where 

Dt theoretical draft intensity created by pressure transformer, inches of water. 
/?f = draft loss due to friction in pressure transformer, inches of water. 
feF = draft loss through the fuel bed, inches of water. 
&B = draft loss through the boiler and setting, inches of water. 
JiEr = draft loss through the breeching, inches of water. 
kv draft loss due to velocity, inches of water. 
&Bd = draft loss due to bends, inches of water. 
he = draft loss due to contraction of opening, inches of water. 
ho = draft loss due to enlargement of opening, inches of water. 
&E == draft loss through the economizer, inches of water. 
&R = draft loss through recuperators, regenerators, or air heaters, inches of water. 

The left hand member of Equation 14 represents the total amount of 
available draft created by the pressure transformer, that is, the natural 
draft chimney, Venturi chimney, or fan, and is equal to the theoretical 
intensity less the internal losses incidental to operation. The right hand 
member represents the sum of all of the various losses of draft throughout 
the entire boiler plant installation outside of the pressure transformer 
itself. The left hand member expresses the available intensity and is 
analogous to the head developed by a centrifugal pump in a water works 
system, while the right hand member expresses the required draft in- 
tensity and is analogous to the total dynamic head in a water works 
system. For a general circulation of gases 

AL - D r (15) 

where 

.Da available draft intensity, inches of water. 
P r = required draft, inches of water. 

The draft loss through the fuel bed (ftp), or the amount of draft required to 
effect a given or required rate of combustion, varies between wide limits 
and represents the greater portion of the required draft. In coal-fired 
installations, the draft loss through the fuel bed is dependent upon the 
following factors: (1) character and condition of the fuel, clean or dirty; 
(2) percentage of ash in the fuel; (3) volume of interstices in the fuel bed, 
coarseness of fuel; (4) thickness of the fuel bed, rate of combustion; 
(5) type of grate or stoker used; (6) efficiency of combustion. 

There is a certain intensity of draft with which the best results will be 
obtained for every kind of coal and rate of combustion. Fig. 8 gives the 
intensity of draft, or the vacuum in the combustion chamber required to 
burn various kinds of coal at various rates of combustion. Expressed in 
other words, these curves represent the amount of draft required to force 
the necessary amount of air through the fuel bed in order to effect various 
rates of combustion. It will be noted that the amount of draft increases 
as the percentage of volatile matter diminishes, being comparatively low 
for the lower grades of bituminous coals and highest for the high grades 
and small sizes of anthracites. Also, when the interstices of the coal are 
large and the particles are not well broken up, as with bituminous coals, 
much less draft is required than when the particles are small and are well 

190 



CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS 



broken up, as with bituminous slack and the small sizes of anthracites. In 
general, the draft loss through the fuel bed increases as: (1) the per- 
centage of volatile matter diminishes; (2) the percentage of fixed carbon 
increases; (3) the thickness of the bed increases; (4) the percentage of ash 
increases; (5) the volume of the interstices diminishes. 

In making the preliminary assumptions for the draft loss through the 
fuel bed, due allowances should be made for a possible future change in 
the grade of fuel to be burned and also in the rate of combustion. A value 



TABLE 1. 



RECOMMENDED MINIMUM CHIMNEY SIZES FOR 
HEATING BOILERS AND FURNACES* 











RECTANGULAR FLUB 


ROUND FLTIK 




WARM Am 


STEAM 


TTT ^ 


NOMINAL 








FtJRNACl 

CAPACITY 

or LEADER 
PTPB 


BOILER 
CAPACITY 
SQFr 
OF RADI- 
ATION 


WATER 
HEATER 
CAPACITY 

or RADI- 
ATION 


DIMEN- 
SIONS or 

FlRVCliAT 

LINING 
IN INCHES 


Actual 
Inside 

of Fire Clay 


Actual 
Area 
Sq In. 


Inside 
Diam- 
eter of 
Lining 
in 


Actual 
Area 
Sq In. 


HEIGHT 
IN FT 
ABOTV 
GRATJB 










in Inches 




Inches 






790 


590 


973 


8^x13 


7 xllJi 


81 






35 


1000 


690 


1,140 








10 


79 






900 


1,490 


13x13 


HJixllJi 


127 










900 


1,490 


8^x18 


6?4 x 16j2 


110 










1,100 


1,820 








12 


113 


40 




1,700 


2,800 


13x18 


HJ^xl6J-i 


183 










1,940 


3,200 








15 


177 






2,130 


3,520 


18x18 


15Jixl5Ji 


248 










2,480 


4,090 


20x20 


17J^xl7}i 


298 






45 




3,150 


5,200 








18 


254 


50 




4,300 


7,100 








20 


314 






4,600 


7,590 


20x24 


17x21 


357 










5,000 


8,250 


24x24 


21x21 


441 






55 




5,570 


9,190 




24x24 


576 






60 




5,580 


9,200 








22 


380 






6,980 


11,500 








24 


452 


65 




7,270 


12,000 




24x28b 


672 










8,700 


14,400 




28x28b 


784 










9,380 


15,500 








27 


573 






10,150 


16,750 




30x30b 


900 










10,470 


17,250 




28x32b 


896 









aTbis table is taken from the A.S.H.V.E. Code of Minimum Requirements for the Heating and Venti- 
lation of Buildings (Edition of 1929). 

bDimensions are for unlined rectangular flues, 

should be selected for this loss which will represent not only the highest 
rate of combustion which will be encountered, but also the grade of coal 
which has the greatest resistance through the fuel bed and which may be 
burned at a later date. 

In powdered-fuel and oil-fired installations, there will be no draft loss 
through the fuel bed since there is none and, consequently, this factor 
becomes zero in the general draft equation. All other factors being 
constant, the height of the chimney in installations of this character will 
be less than the height in coal-fired installations, and in the case of me- 
chanical draft installations the driving units need not be as large since the 
head against which the fan is to operate is not as great in the former as 
in the latter. 

191 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



The draft loss through the boiler and setting (As) also varies between wide 
limits and, in general, depends upon the following factors: 

1. Type of boiler. 5. Arrangement of baffles. 

2. Size of boiler. 6. Type of grate. 

3. Rate of operation. 7. Design of brickwork setting. 

4. Arrangement of tubes. 8. Excess air admitted. 

9. Location of entrance into breeching. 

Curves showing the draft loss through the boiler are usually based on 
the load or quantity of gases passing through the boiler, expressed in 
terms of percentage of normal rate of operation. Owing to the great 
variety of boilers of different designs and the various schemes of baffling, 
it is impossible to group together a set of curves for the draft loss through 




5 10 15 20 25 30 35 40 45 

POUNDS OF COAL BURNED PER SQ FT OF GRATE SURFACE PER HOUR 

FIG. 8. DRAFT REQUIRED AT DIFFERENT RATES OF COMBUSTION 
FOR VARIOUS KINDS OF COAL 

the boiler which may even be used generally. It is therefore necessary to 
secure this information from the manufacturer of the particular type of 
boiler and baffle arrangement under consideration. 

When a boiler is installed and in operation, the draft loss depends upon 
the amount of gases flowing through it. This, in turn, depends upon the 
proportion of excess air admitted for combustion. Primarily, the amount 
of excess air is measured by the CO Z content; the less the amount of C0 2 , 
the greater the amount of excess air and hence the greater the draft loss. 

The loss of draft through the boiler will vary directly as the size of the 
boiler and the length of the gas passages within. The loss also varies as 
the number of tubes high, but not in a direct ratio inasmuch as the loss 
due to the reversal of flow at the ends of the baffles remains constant 
regardless of the height of the boiler. The arrangement of the tubes, 
whether the gases flow parallel to or at right angles to the tubes, has an 
appreciable effect on the loss. The arrangement of the baffles influences 
the draft loss greatly, the loss through a boiler with five passes being 

192 



CHAPTER 10. CHIMNEYS AND DRAFT CAIICULATIONS 

greater than the loss through one of three or four passes. A poor design 
and a rough condition of the brickwork will increase the loss greatly, 
whereas a proper design and a smooth condition will keep the loss at a 
minimum. The loss through the boiler will be less when the breeching 
entrance is located at or near the top of the boiler than when it is located 
at or near the bottom since the gases have a shorter distance to travel 
in the former instance. 

The draft loss through the breeching (&Br) is given by the general 
equation : 



where 

W = the amount of gases flowing, pounds per second. 

T c = absolute temperature of breeching gases, degrees Fahrenheit. 

/ = coefficient of friction. 

L length of breeching, feet. 

A = area of breeching, square feet. 

BQ = atmospheric pressure corresponding to altitude, inches of mercury. 
W c = weight of a cubic foot of breeching gases at F and sea level atmospheric 

pressure; pounds per cubic foot. 
Cbr = hydraulic radius of breeching section. 

It has been the general custom to lump off the intensity of the breeching 
loss at 0.10 in. of water per 100 ft of breeching length regardless of its size 
or shape or the amount and temperature of the gases flowing through it. 
This practice is hazardous and has no more foundation in fact than that of 
determining the friction head in a water works system without taking 
into consideration the size of the pipe or the amount of water flowing 
through it. When the length of the breeching is relatively short, any 
variation in any one of the factors in the equation will have no appreciable 
effect on the draft loss. However, when the breeching is relatively long, 
the draft loss is affected greatly by the various factors, particularly by the 
size and shape as well as by the weight of gases flowing. 

The draft loss due to velocity (hv) is given by the equation 

0.000194Wr c 

hv = 



and represents the amount of draft required to accelerate the gases from 
zero velocity to the velocity at which the gases are flowing, or in other 
words, from a static gas condition of zero flow to the amount of gases 
flowing throughout the installation. This loss corresponds to the velocity 
head in water works systems. 

The draft loss due to bends (&Bd) is equivalent to the loss due to the 
velocity head for a 90-deg bend. In changing direction of flow, the gas 
velocity decreases to zero with a loss of velocity head and then increases 
to its proper value at the expense of a loss in pressure head, the net result 
being a loss in pressure head equal to the velocity head at the bend. 
This loss is given by the equation: 



193 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

The friction at a right-angle bend is sometimes expressed as the 
equivalent of a straight length of flue of a certain length for a certain 
diameter, similar to the procedure used in estimating the loss due to 
bends in piping systems conducting water. Most flues, however, par- 
ticularly breechings, are built square or rectangular in section and no 
general equation based on the shape of the flue can be conveniently 
expressed. 

The draft loss due to sudden contraction of an area (he) is given by the 
equation : 



C = A* 9 B W C 
where 

JT C coefficient of sudden contraction based on -, the ratio of the areas of the 



smaller to the larger section = 0.5 { 1 r- j 



A s = area of the smaller section. 

When the flue or passage through which the gases flow is suddenly 
contracted, a considerable portion of the static head in the larger section 
is converted into velocity head and a draft loss of some consequence, par- 
ticularly in a short breeching, takes place. A sudden contraction should 
always be avoided where possible. At times, however, due to obstruc- 
tions or limited head-room, it is necessary to alter the size of the breeching, 
but a sudden contraction may be avoided by gradually decreasing the 
area over a length of several feet. 

The draft loss due to a sudden enlargement of an area (ho) is given by the 
equation : 



where 

K = coefficient of sudden enlargement based on -^, the ratio of the areas of the 



small 



ter to the larger section = f 1 - -p J 



When the flue or passage through which the gases flow is suddenly 
enlarged, a portion of the velocity head is converted into static head in the 
larger section and, like the loss due to sudden contraction, a loss of some 
consequence, particularly in short breechings, takes place. A sudden 
enlargement in a breeching may be avoided by gradually increasing the 
area over a length of several feet. In large masonry chimneys, the area of 
the flue at the region of the breeching entrance is considerably larger 
than the area of the breeching at the chimney, and a sudden enlargement 
exists. 

The draft loss through the economizer (&E) should be obtained from the 
manufacturer but for general purposes it may be computed from the 
following general equation : 



ft. = ' c (31) 

10* 

194 



CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS 

where 

W n = pounds of gases flowing per hour per linear foot of pipe in each economizer 

section. 
N number of economizer sections. 

An economizer in a steam plant affects the draft in two ways, (1) it 
offers a resistance to the flow of gases, and (2) it lowers the average 
chimney gas temperature, thereby decreasing the available intensity. In 
the case of a natural draft installation, both of these factors result in a 
relative increase in the height of the chimney and, in the case of a large 
plant, they may add as much as 20 or 30 ft to the height. The decrease 
in the temperature of the gases after they have passed through the 
economizer has an extremely important effect on the performance of a 
natural draft chimney and also upon the performance of a fan. 

CpNSTHUCTION DETAILS 

For general data on the construction of chimneys reference should be 
made to the Standard Ordinance for Chimney Construction of the 
National Board of Fire Underwriters. Briefly summarized, these provisions 
are as follows for heating boilers and furnaces: 

The construction, location, height and area of the chimney to which a heating boiler 
or warm-air furnace is connected affect the operation of the entire heating system. Most 
residence chimneys are built of brick and may be either lined or unlined, but in either 
case the walls must be air-tight and there should be only one smoke opening into the 
chimney. Cleanout, if provided, must be absolutely air-tight when closed. 

The walls of brick chimneys shall be not less than 3% in. thick (width of a standard 
size brick) and shall be lined with fire-clay flue lining. Fire-clay flue linings shall be 
manufactured from suitable refractory clay, either natural or compounded, and shall 
be adapted to withstand high temperatures and the action of flue gases. They shall be 
of standard commercial thickness, but not less than % in. All fire-clay flue linings shall 
meet the standard specification of the Eastern Clay Products Association. The flue 
sections shall be set in special mortar, and shall have the joints struck smooth on the 
inside. The masonry shall be built around each section of lining as it is placed, and all 
spaces between masonry and linings shall be completely filled with mortar. No broken 
flue lining shall be used. Flue lining shall start at least 4 in. below the bottom of smoke- 
pipe intakes of flues, and shall be continued the entire heights of the^flues and project 
at least 4 in. above the chimney top to allow for a 2 in. projection of lining. The wash or 
splay shall be formed of a rich cement mortar. To improve the draft the wash surface 
should be concave wherever practical. 

Flue lining may be omitted in brick chimneys, provided the walls of the chimneys 
are not less than 8 in. thick, and that the inner course shall be a refractory clay brick. 
All brickwork shall be laid in spread mortar, with all joints push-filled. Exposed joints 
both inside and outside shall be struck smooth. No plaster lining shall be permitted. 

Chimneys shall extend at least 3 ft above flat roofs and 2 ft above the ridges of peak 
roofs when such flat roofs or peaks are within 30 ft of the chimney. The chimney 
shall be high enough so that the wind from any direction shall not stnke the top of the 
chimney from an angle above the horizontal. The chimney shall be properly capped with 
stone, terra cotta, concrete, cast-iron, or other approved material; but no such cap 
or coping shall decrease the flue area. 

There shall be but one connection to the flue to which the boiler or furnace smoke- 
pipe is attached. The boiler or furnace smoke-pipe shall be thoroughly grouted into the 
chimney and shall not project beyond the inner surface of the flue lining. 

The size or area of flue lining or of brick flue for warm-air furnaces depends on height 
of chimney and capacity of heating system. For chimneys not less than 35 ft in height 
above grate line, the net internal dimensions of lining should be at least 7 x 11 H in. 

195 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



for a total leader pipe area up to 790 sq in. Above 790 and up to 1,000 sq in. of leader 
pipe area the lining should be at least 11^ x 11 % in. inside. In case of brick flues not 
less than 35 ft in height with no linings, the internal dimensions should be at least 
8 x 12 in. up to 790 sq in. of leader area, and at least 12 x 12 in. for leader capacities up to 
1,000 sq in. Chimneys under 35 ft in height are unsatisfactory in operation and hence 
should be avoided. 

CHIMNEYS FOR GAS HEATING 

The burning of gas differs from the burning of coal in that the force 
which supplies the air for combustion of the gas comes largely from the 
pressure of the gas in the supply pipe, whereas air is supplied to a bed of 
burning coal by the force of the chimney draft. If, with a coal-burning 
boiler, the draft is poor, or if the chimney is stopped, the fire is smothered 
and the combustion rate reduced. In a gas boiler or furnace such a 
condition would interfere with the combustion of the gas, but the gas 
would continue to pass to the burners and the resulting incomplete com- 
bustion would produce a dangerous condition. In order to prevent incom- 
plete combustion from insufficient draft, all gas-fired boilers and furnaces 
should have a back-draft diverter in the flue connection to the chimney. 

TABLE 2. SUGGESTED GENERAL DIMENSIONS FOR VERTICAL BACK-DRAFT DIVERTER 




Table of Dimensions (In.) 



PIPE 
SIZE 


A 


B 


C 


D 


E 


P 


G 


H 


I 


J 


K 


L 


M 


3 


3 


3 


5.5 


7.0 


3.8 


0.7 


4.4 


3.0 


1.5 


2.5 


0.7 


1.5 


2.3 


4 


4 


4 


7.2 


9.5 


5.0 


1.0 


6.0 


4.0 


2.0 


3.5 


1.0 


2.0 


3.0 


5 


5 


5 


9.4 


10.8 


5.3 


1.5 


8.0 


5.0 


2.3 


4.0 


0.9 


2.4 


3.5 


6 


6 


6 


11.5 


12.0 


5.6 


1.9 


9.8 


6.0 


2.5 


4.5 


0.8 


2.7 


4.0 


7 


7 


7 


13.5 


13.9 


6.4 


2.3 


11.6 


7.0 


2.9 


5.3 


0.9 


3.1 


4.6 


8 


8 


8 


15.5 


15.8 


7.1 


2.7 


13.4 


8.0 


3.2 


6.0 


1.0 


3.5 


5.3 


9 


9 


9 


17.5 


17.5 


7.7 


3.1 


15.2 


9.0 


3.5 


6.7 


1.0 


4.0 


5.8 


10 


10 


10 


19.7 


18.8 


7.9 


3.6 


17.2 


10.0 


3.8 


7.3 


1.0 


4.3 


6.2 


11 


11 


11 


22.2 


20.7 


8.4 


4.3 


19.6 


11.0 


4.1 


8.0 


1.5 


4.6 


6.6 


12 


12 


12 


24.7 


22.2 


8.7 


5.0 


22.0 


12.0 


4.4 


8.5 


1.7 


5.0 


7,0 



196 



CHAPTER 10. CHIMNEYS AND DRAFT CALCUIATIONS 



A study of a typical back-draft diverter shows that partial or complete 
chimney stoppage^will merely cause some of the products of combustion 
to be vented out into the boiler room, but will not interfere with com- 
bustion^ In fact, gas-designed appliances must perform safely under such 
a condition to be approved by the American Gas Association Laboratory. 
Other functions of the back-draft diverter are to protect the burner and 
pilot from the effects of down-drafts, and to neutralize the effects of 
variable chimney drafts, thus maintaining the appliance efficiency at a 
substantially constant value. Converted boilers or furnaces, as well as 
gas-designed appliances, should be provided with back-draft diverters. 

Since back-draft diverters have a special function to perform in pro- 
tecting gas burning appliances, it is necessary that they should be built 
to the proper size as shown in Table 2 for a vertical type and in Table 3 
for a horizontal arrangement. Equipment of this kind listed by the 
American Gas Association Testing Laboratory must bear the listing 
symbol A.G.A. 



. SUG 


GESTED GENERAL DIMENSIONS FOR HORIZONTAL BACK-DRAFT DIVERTER 












t 
, r ,._ tei n 


1 
[ 


i 
) 


r" 


~i 


^ /-Baffle 
1 / / 








r 


^ 




E 




E 


3 


( 






1-\- 1 

L 

Baffle 


^ \ 

Baffle 
strap 


nlet 





-Relief opening *^ 

Table of Dimensions (In.) 



PIPE 

SIZE 


A 


B 


C 


D 


E 


F 


G 


H 


I 


J 


E 


L 


M 


3 


3 


3 


6 


1.5 


4.8 


3.8 


1.4 


2.5 


2,5 


2.5 


2.1 


6 


1.8 


4 


4 


4 


8 


2.0 


4.8 


5.0 


1.9 


3.4 


3.4 


3.4 


2.9 


0.8 


2.3 


5 


5 


5 


10 


2.5 


4.8 


6.3 


2.4 


4.2 


4.2 


4.2 


3.5 


0.9 


2.9 


6 


6 


6 


12 


3.0 


4.8 


7.5 


2.9 


5.0 


5.0 


5.0 


4.3 


1.1 


3.5 


7 


7 


7 


14 


3.5 


4.8 


8.8 


3.4 


5.9 


5.9 


5.9 


5.0 


1.3 


4.1 


8 


8 


8 


16 


4.0 


4.8 


10.0 


3.9 


6.7 


6.7 


6.7 


5.6 


1.5 


4.7 


9 


9 


9 


18 


4.5 


4.8 


11.3 


4.4 


7.5 


7.5 


7.5 


6.4 


1.7 


5.3 


10 


10 


10 


20 


5.0 


4.8 


12.5 


4.9 


8.4 


8.4 


8.4 


7.0 


1.9 


5.8 


11 


11 


11 


22 


5.5 


4.8 


13.8 


5.4 


9.2 


9.2 


9.2 


7.8 


2.1 


6.4 


12 


12 


12 


24 


6.0 


4.8 


15.0 


5.9 


10.0 


10.0 


10.0 


8.5 


2.3 


7.0 



197 



HEATING VENTIUITING AIR CONDITIONING GUIDE 1938 



As is the case with the complete combustion of almost all fuels, the 
products of combustion for gas are carbon dioxide (C0 9 ) and water vapor 
with just a trace of sulphur tripxide (50 3 ). Sulphur usually burns to the 
trioxide in the presence of an iron oxide catalyst. The volume of water 
vapor in the flue products is about twice the volume of the carbon dioxide 
when coke oven or natural gas is burned. Because of the large quantity 
of water vapor which is formed by the burning of gas, it is quite important 
that all gas-fired central heating plants be connected to a chimney having 
a good draf t.^ Lack of chimney draft causes stagnation of the products of 
combustion in the chimney and results in the condensation of a large 
amount of the water vapor. A good chimney draft draws air into the 
chimney through the openings in the back-draft diverter, lowers the dew 
point of the mixture, and reduces the tendency of the water vapor to 
condense. 

The flue connections from a gas-fired boiler or furnace to the chimney 
should be of a non-corrosive material. In localities where the price of 

TABLE 4. MINIMUM ROUND CHIMNEY DIAMETERS FOR GAS APPLIANCES (INCHES) 



HJCIOHT or 


GAS CONSUMPTION m THOUSANDS OF Bin PER HOTJB 


FZZT 


100 


200 


300 


400 


500 


750 


1000 


1500 


2000 


20 


4.50 


5.70 


6.60 


7.30 


8.00 


9.40 


10.50 


12.35 


13.85 


40 


4.25 


5.50 


6.40 


7.10 


7.80 


9.15 


10.25 


12.10 


13.55 


60 


4.10 


5.35 


6.20 


6.90 


7.60 


8.90 


10.00 


11.85 


13.25 


80 


4.00 


5.20 


6.00 


6.70 


7.35 


8.65 


9.75 


11.50 


12.85 


100 


3.90 


5.00 


5.90 


6.50 


7.20 


8.40 


9.40 


11.00 


12.40 



gas requires the use of highly efficient appliances, the material used for 
the flue connection not only should be resistant to the corrosion of water, 
but should resist the corrosion of dilute solutions of sulphur trioxide in 
water. Local practice should be followed in the selection of the most 
appropriate flue materials. 

When condensation in a chimney proves troublesome, it may be 
necessary to provide a drain to a dry well or sewer. The cause of the 
excessive condensation should be investigated and remedied if possible. 
This may be done by raising the flue temperature slightly or increasing 
the size of the back-draft diverten The protection of unlined chimneys 
has been investigated and the results indicate that after the loose material 
has been removed, the spraying with a water emulsion of asphalt- 
chromate provides an excellent protection, 

A chimney for a gas-fired boiler or furnace should be constructed in 
accordance with the principles applicable to other boilers. Where the 
wall forming a smoke flue is made up of less than an 8-in. thickness of 
brick, concrete, or stone, a burnt fire-day flue tile lining should be used. 
Care^ should be used that the lengths of flue tile meet properly with no 
openings at the joints. Cement mortar should be used for the entire 
chimney. 

Table 4 gives the minimum cross-sectional diameters of round chim- 

198 



CHAPTER 10. CHIMNEYS AND DRAFT CALCULATIONS 

neys (in inches) for various^ amounts of heat supplied to the appliance, 
and for various chimney heights. This is in accordance with American 
Gas Association recommendations. 



PROBLEMS IN PRACTICE 

1 What are the principle factors influencing the intensity of natural draft? 

The intensity of natural draft depends largely upon the height of chimney above the 
grate bar level and the temperature difference between the chimney gases and the 
atmosphere. 

2 What two kinds of draft need he considered? 

Natural draft caused by temperature differences, and artificial draft caused by me- 
chanical forcing. 

3 What is the effective height of a chimney? 

The height from the grate level to the top of the chimney is the effective height in pro- 
ducing natural draft. 

4 What dual purpose does a tall chimney fulfill? 

A tall chimney primarily creates the necessary draft to move the air required for the 
combustion process and to move the products of combustion, and secondarily it dis- 
charges the gases at a high elevation to prevent them from becoming a nuisance. 

5 What is the direct influence of the height on the design of a chimney? 

The immediate purpose of height is to provide that draft intensity under the conditions 
of chimney gas temperature such that it will be adequate to overcome all the frictional 
resistances of the installation, as well as to provide for the actual gas movement. 



6 Of what importance is chimney cross-sectional area in stack design? 

The area should be as large as is economically feasible in order that the frictional loss 

for the chimney he 

in overcoming the i 



for the chimney height should not destroy the effectiveness of the height-created draft 
he necessary frictional resistances of the boiler and its flue connections. 



7 Of what importance is the Reynolds number in chimney design? 

It permits the selection of a more specific value of the chimney friction factor, rather 
than a general one, to correspond with conditions of size, nature of the gas, rate of gas 
flow, and condition of the surface. 

8 a. Name the principle advantages of natural draft. 

b. Name the principle disadvantages of natural draft. 

a. Simplicity, reliability, freedom from mechanical parts, low cost of maintenance, 
relatively long life, relatively low depreciation, operation with no power requirement. 

b. Lack of flexibility, irregularity, dependence on surroundings, susceptibility to tem- 
perature changes. 

9 How is mechanical draft created? 

By forced draft, by induced-draft fans, or by a Venturi chimney. 

10 Distinguish between theoretical and available draft. 

Theoretical draft is the difference in pressure inside and outside the base of a chimney 
when it is under operating temperatures but when there are no gases flowing. Available 
draft is less than theoretical draft by the friction loss due to the flow of gases through 
the chimney. 

199 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

11 Explain the term efficiency of a natural draft chimney. 

The efficiency of a chimney is the ratio of the work it does in moving gases to the theo- 
retical amount of power it generates. 

12 How is the available draft used in a heating plant? 

The available draft at the base of the chimney is used to overcome the loss in pressure 
through the grate, the fuel bed, the boiler passes, the breeching. 

13 What are some of the factors that influence the draft loss through the fuel 
bed? 

Uniformity and size of coal, the amount of ash mixed with the fuel on the grate, thickness 
of fuel bed, rate of combustion, amount of air supply as related to the coal burning rate. 

14 How does the volatile matter content affect the draft loss through the fuel 
bed? 

The higher the volatile content and the lower the fixed carbon content, the lower the 
draft loss. 

15 In what cases will there he no fuel bed draft loss? 

In oil, gas, and powdered fuel firing the fuel is mixed and burned in suspension; con- 
sequently, no measurable resistance is encountered in the combustion zone. 

16 Is it possible to state an average value for the draft loss through a boiler 
and its setting? 

No. The draft loss varies widely and depends on many factors such as the size and type 
of gas passageways. The manufacturer is usually able to supply such information. 

17 Of what significance is the CDs content of stack gases in establishing 
draft loss? 

The COz content of the exit gases is a measure of the completeness of the combustion and 
the amount of excess air supplied. Low COj indicates a high excess of air and hence 
a high draft loss. 

18 What two effects does an economizer have on the draft loss? 

An economizer offers resistance to the flow of gases over the added surfaces; it lowers the 
temperature of the gases going to the chimney and therefore decreases the available 
draft. This decrease often necessitates the addition of forced draft. 

19 What main provisions should be considered in good chimney construction? 

Chimneys should be air-tight and connected to only one smoke opening. The chimney 
top should be high enough above surroundings so the wind will not strike it at any angle 
above the horizontal. ^ Chimney walls should be not less than one brick in width, and 
they should be lined with fire-clay tile of the size required for the attached heating unit. 
Tile lining sizes are stated as outside dimensions; therefore, their effective dimensions 
are less by the thickness of the wall. 

20 What is the purpose of a back draft diverter as used on gas burning units? 

Since the fuel is supplied under pressure independent of draft it is necessary to free the 
unit from the variable chimney draft and to supply air for combustion in direct propor- 
tion to the supply of fuel gas. The back draft diverter protects the pilot and burners 
from down drafts. 



200 



Chapter 11 

AUTOMATIC FUEL BURNING EQUIPMENT 

Classification of Stokers, Combustion Process and Adjustments, 

Furnace Design, Classification of Oil Burners, Combustion 

Chamber Design, Classification of Gas-Fired Appliances 

A UTOMATIC mechanical equipment for the combustion of solid, 
f\ liquid and gaseous fuels is considered in this chapter. 

MECHANICAL STOKERS 

A mechanical stoker is a device that feeds a solid fuel into a combustion 
chamber, provides a supply of air for burning the fuel under automatic 
control and, in some cases, incorporates a means of removing the ash and 
refuse of combustion automatically. Coal can be burned more efficiently 
by a mechanical stoker than by hand firing because the stoker provides a 
uniform rate of fuel feed, better distribution in the fuel bed and positive 
control of the air supplied for combustion. 

Stokers may be divided into four types according to their construction, 
namely, (1) overfeed flat grate, (2) overfeed inclined grate, (3) underfeed 
side cleaning type, and (4) underfeed rear cleaning type. 

Overfeed Flat Grate Stokers 

This type is represented by the various chain- or traveling-grate stokers. 
These stokers receive fuel at the front of the grate in a layer of uniform 
thickness and move it back horizontally to the rear of the furnace. Air is 
supplied under the moving grate to carry on combustion at a sufficient 
rate to complete the burning of the coal near the rear of the furnace. 
The ash is carried over the back end of the stoker into an ashpit beneath. 
This type of stoker is suitable for small sizes of anthracite or coke breeze 
and also for bituminous coals, the characteristics of which make it 
desirable to bum the fuel without disturbing it. This type of stoker 
requires an arch, over the front of the stoker to maintain ignition of the 
incoming fuel. Frequently, a rear combustion arch is required to main- 
tain ignition until the fuel is fully consumed. A typical traveling-grate 
stoker is illustrated in Fig. 1. 

Another and distinct type of overfeed flat-grate stoker is the 
spreader (Fig., 2) or sprinkler type in which coal is distributed either 
mechanically or by air over the entire grate surface. This type of stoker 
has a wide application on small sized fuels and on certain special fuels 
such as lignites, high-ash coals, and coke breeze. 

201 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Overfeed Inclined Grate Stokers 

In general the combustion principle is similar to the flat grate stoker, 
but this stoker (Fig. 3) is provided with rocking grates set on an incline to 
advance the fuel during combustion. Also this type is provided with an 
ash plate where ash is accumulated and from which it is dumped periodi- 
cally. This type of stoker is suitable for all types of coking fuels but 
preferably for those of low volatile content. Its grate action has the 
tendency to keep the fuel bed well broken up thereby allowing for free 



I I I T T 




FIG. 1. OVERFEED TRAVELING-GRATE STOKER 
Coal conveying pipe 

^ 

Burner nozzle 




FIG. 2. SPREADER STOKER-PNEUMATIC TYPE 

passage of air. Because of its agitating effect on the fuel it is not so 
desirable for badly clinkering coals. Furthermore, it should usually be 
provided with a front arch to care for the volatile gases. 

Underfeed Side Cleaning Stokers 

In this type (Fig. 4), the fuel is introduced at the front of the furnace to 
one or more retorts, is advanced away from the retort as combustion 
progresses, while finally the ash is disposed of at the sides. This type of 
stoker is suitable for all coking coals while in the smaller sizes it is suitable 
for small sizes of anthracites. In this type of stoker the fuel is delivered 
to a retort beneath the fire and is raised into the fire. During this process 

202 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

the volatile gases are released, are mixed with air, and pass through the 
fire where they are burned. The ash may be continuously discharged as 
in the small stoker or may be accumulated on a dump plate and periodi- 
cally discharged. This stoker requires no arch as it automatically pro- 
vides for the combustion of the volatile gases. 




Secondary- 



I fof Ignited and partuHy coked fuel 




FIG. 3. OVERFEED INCLINED GRATE STOKER 




FIG. 4. UNDERFEED PLUNGER TYPE STOKER 

Underfeed Rear Cleaning Stokers 

This type of stoker accomplishes combustion in much the same manner 
as the side cleaning type, but consists of several retorts placed side by side 
and filling up the furnace width, while the ash disposal is at the rear. In 
principle, its operation is the same as the side cleaning underfeed. 

203 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

Stokers also may be classified according to their size based upon coal 
feed rates. The following classification has been made by the United 
States Department of Commerce in cooperation with the Stoker Manu- 
facturers' Association'. 

Class 1. Up to and including 60 Ib of coal per hour. 
Class 2. 60 to 100 Ib of coal per hour. 
Class 3. 100 to 300 Ib of coal per hour. 
Class 4. 300 to 1200 Ib of coal per hour. 

(A fifth class is included covering stokers having a feeding capacity above 1200 Ib 
of coal per hour). 

Class 1 and Class 2 Stokers, Household 

Since these stokers are used primarily for home heating, it is desirable 
that their design be simple and attractive in appearance, and that they be 
quiet and automatic in .operation. 

A common type of stoker in this class consists, essentially of a coal 
reservoir or hopper, a screw for conveying the fuel from the hopper to the 
burner head or retort; a fan which supplies the air for combustion, a 




FIG. 5. UNDERFEED SCREW STOKER, HOPPER TYPE 



transmission for driving the coal feed worm, and an electric motor or 
motors for supplying the motive power for both coal feed and air supply 
as indicated in Fig. 5. The shape of the retort in this class of stokers is 
usually round although rectangular retorts are favored by some manu- 
facturers. In all cases, however, the retort incorporates tuyeres through 
which the air for combustion is admitted. 

Some household stokers are provided with an automatic grate-shaking 
mechanism together with screw conveyors for removing the ash from the 
ashpit (Fig. 6) and depositing it in an ash receptacle outside the boiler. 

Certain types can also be provided with a coal conveyor which takes 
coal from the storage bin and maintains a full hopper at the stoker. In 
some cases the coal bin functions as the stoker hopper as shown in Fig. 7, 
and an extended worm is used to convey the fuel to the combustion furnace. 
. Domestic stokers may feed coal to the furnace either intermittently or 
with a continuous flow regulated automatically to suit conditions. 

Household stokers are made for ail classes of fuel ^anthracite, bitu- 
minous and semi-bituminous coals, and coke. The United States Depart- 

204 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

went of Commerce has issued commercial standards for household anthra- 
cite burners, which may be obtained by application. Standards of 
performance for bituminous coal stokers are also being developed by 
Bituminous Coal Research, Inc. The standards for anthracite stokers are 
described in the next paragraphs. 

Operating Requirements for Anthracite Stokers 

Efficiency. The over-all efficiency of the unit at all points above 50 per cent of maxi- 
mum coal feed shall be above 50 per cent when installed in a round sectional cast-iron 
boiler having three intermediate sections and 1H in. of asbestos insulation or its equiva- 




FIG. 6. UNDERFEED SCREW STOKER WITH AUTOMATIC ASH REMOVAL 



tf 




FIG. 7. UNDERFEED SCREW STOKER, BIN FEED TYPE 



lent in good condition of repair, operating at 50 per cent or more of the boiler capacity. 
The efficiency shall be maintained for any continuous period of 4 hours during any test 
or observation run. 

Ash Loss. Combustible in ash shall not exceed 7.5 per cent of the Btu content of the 
coal as fired at any rate of coal feed above 50 per cent of maximum. Methods of test 
according to Code No. 3 of the A.S.H.V.E. 1 are to be followed in all details applicable 
to stoker testing. 

Clinker. Ash removing systems should at all times be capable of disposing of any 
clinker which may be formed under any conditions of operation with the coals prescribed. 



*A..S.H.V.E. Performance Test Code for Steam Heating Solid Fuel Boilers (Code 3), (A.S.H.V.E. 
TRANSACTIONS, Vol. 35, 1929, p. 332). 

205 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Combustion Rate. A combustion rate of at least 13 Ib per square foot of horizontal 
projected area of ash ring per hour must be continuously maintained for at least 9 hours 
with the above conditions of efficiency, ash and clinker. 

Flue Gas. Flue gas shall be not below 6 per cent in carbon dioxide with a reasonably 
tight boiler at any rate of operation above 50 per cent of maximum coal feed. 

Maximum Rating^ The maximum rating, in terms of gross square feet of water or 
steam radiation which the burner will supply, when intended for installation in the 
average existing cast-iron boiler, shall be 90 per cent of the maximum steam produced in 
a round cast-iron boiler in good repair having three intermediate sections and the 
equivalent of 1J in. of asbestos insulation. However, in no case shall the maximum 
rating be greater than 29 sq ft of direct steam radiation for each pound of coal fired per 
hour, and in no case shall ratings be based upon efficiency figures below 50 per cent. 

The maximum rating as defined in the preceding paragraph shall be based upon com- 
bustion of Pennsylvania anthracite having the following approximate analysis: 

Volatile matter 3.5 to 9 per cent ; ash content not to exceed 15 per cent ; sulphur content 
under 1.5 per cent; ash fusing temperature 2750 F, or above (volatile, ash and sulphur 
content on dry basis in accordance with A.S.T.M. method D271-33) ; Btu content 12,000 
or above; properly sized as follows: A No. 1 buckwheat should pass through a round 
mesh screen having %6 i n - holes and over a similar screen having 5ie m - holes. The 
undersizing should not exceed 15 per cent and the oversizing should not exceed 10 per 
cent. A No. 2 buckwheat (rice) should pass through a round mesh screen having holes 
5ie in. in diameter and over a like screen having holes of %e in. in diameter. The under- 
sizing should not exceed 15 per cent and the oversizing should not exceed 10 per cent. 

Coal Storage. It is recommended that the coal bin or closet be constructed so as to 
be dustproof. 

Electrical Consumption. The electrical consumption shall not exceed 18 kwh per 
2000 Ib of coal burned at any rate of coal feed above 50 per cent of the maximum. 

Operation Upon Other Sizes of Coal. The foregoing specifications have been drafted 
for operating with the Nos. 1 and 2 buckwheat sizes of anthracite. In the event that 
other sizes are recommended, ratings shall be based upon the same efficiency and ash 
loss requirements. 

Banking. The burner shall be so constructed or controlled as to maintain a fire 
during an indefinite banking period. 

Acceleration. When the burner resumes operation after a 12 hour banking period, the 
time required for the stack temperature to reach a normal maximum shall not exceed 
60 min. 

Stoker-Fired Units 

Boilers and air conditioners especially designed for stokers are now 
becoming available. Present designs feature better coordination between 
the heat absorber and the stoker. Increased setting height and furnace 
volume and more heating surface than in conversion installations are 
usually to be found in these stoker units. 

Class 3 Stokers, Apartment House, Small Commercial 

This class is used extensively for heating plants in apartments and 
hotels, and also for small industrial plants such as laundries, bakeries, and 
creameries. The majority of stokers used in this field are of the underfeed 
type. The principal exception is an overfeed type having step action 
grates in a horizontal plane and so arranged that they are alternately 
moving and stationary, and are designed to advance the fuel during com- 
bustion to an ash plate at the rear. 

All of the stokers are provided with a coal hopper outside of the boiler. 
In the underfeed types, the coal feed from this hopper to the furnace may 
be accomplished by a continuously revolving screw or by an intermittent 

206 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

plunger. The drive for the coal feed may be an electric motor, or a steam 
or hydraulic cylinder. With an electric motor, the connection between 
the driver and the coal feed may be through a variable speed gear train 
which provides two or more speeds for the coal feed; or it may be through 
a simple gear train and a variable speed driver for the change in speed of 
the coal feed; or a simple gear train with a coal feed having an adjustment 
for varying the travel of the feeding device. With a steam or hydraulic 
cylinder, the power piston is connected directly to the coal feeding 
plunger. 

The stokers in this class vary also in their retort design according to the 
fuels and load conditions. The retort is placed approximately in the 
middle of the furnace and is provided with tuyere openings at the top on 
all sides. In the plunger-feed type the retort extends from the inside of 
the front wall entirely to the rear wall or to within a short distance of the 
rear wall. This type of retort has tuyeres on the sides and at the rear. 

These stokers also differ in the grate surface surrounding the retort. 
In many of the worm-feed stokers this grate is entirely a dead plate on 
which the fuel rests while combustion is completed. In the dead-plate 
type, all of the air for combustion is furnished by the tuyeres at the retort. 
Because of this, combustion is well advanced over the retort so that it 
may easily be completed by the air which percolates through the fuel bed. 
With the dead-plate type of grate the ash is removed through the fire 
doors and it is therefore desirable that the fuel used shall be one in which 
the ash is readily reduced to a clinker at the furnace temperature, in 
order that it may be removed with the least disturbance of the fuel bed. 

In other stokers in this class, the grates outside of the retort are air- 
admitting and some stokers have shaking grates. These grates permit a 
large part of the ash to be shaken into the ashpit beneath, while the 
clinkers are removed through the fire doors. With this type of grate, the 
main air chamber extends only under the retort while the side grates 
receive air by natural draft from the ashpit. 

In still other stokers of this class, the main air chamber extends beyond 
the retort and is covered with fuel-bearing, air-supplying grates. With 
this type of grate, the fuel is supplied with air from the main air chamber 
throughout combustion. Also with this type of grate, dump plates are 
provided beyond the grates where the ash accumulates and from which it 
can be dropped periodically into the ashpit beneath. 

Stokers in this class are compactly built in order that they may fit into 
standard heating boilers and still leave room for sufficient combustion 
space above the grates. The height of the grate is approximately the same 
as that of the ordinary grates of boilers, so that it is usually possible to 
install such stokers with but minor changes in the existing equipment. 
In some districts, there are statutory regulations governing such settings. 

These stokers vary in furnace dimensions from 30 in. square to approxi- 
mately 66 in. square. The capacity of the stokers is measured by the 
amount of coal that can be burned per hour. In general, manufacturers 
recommend that, for continuous operation, the coal burning rate shall not 
exceed 25 Ib of coal per square foot of grate per hour, while for short 
peaks this rate may be increased to 30 Ib per hour. Although these 
stokers were designed to burn bituminous coal, types are available for 

207 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



the semi-bituminous coals such as Pocahontas and New River. They can 
also be used to burn the small sizes of anthracite but at a somewhat 
lower rate. 

Class 4 Stokers, Medium Commerial 

These stokers are usually of the screw feed type without auxiliary 
plungers or other means of distributing the coal. Rectangular retorts 
with sectional tuyeres and dead plates without air ports are employed. 
The unit type of construction is almost universally used, the unit incor- 
porating the hopper, the transmission for driving the feed screw, and the 
fan for supplying air for combustion. 

Class 4 Stokers, Large Commercial, Small High Pressure Plants 

Stokers in this group vary widely in details of mechanical design and 
the several methods of feeding coal previously described may be employed 
Such methods of applying power to the fuel conveying mechanism as, 
continuous gear train transmission, ratchet type speed reducer, hydraulic 
cylinder and steam cylinder are used. Varying methods of ash disposal 
are found in this class. 

Large Stokers 

This class includes stokers with hourly burning rates of over 1200 Ib 
of coal per hour. The prevalent stokers in this field are : 

a. Overfeed flat grate stokers. 

b. Overfeed inclined grate stokers. 

c. Underfeed side cleaning stokers. 

d. Underfeed rear cleaning stokers. 

Overfeed inclined grate stokers are seldom built in sizes of over 500 hp 
and are not as extensively used as other types of stokers. 

Underfeed side cleaning stokers are made in sizes up to approximately 
500 hp and in this field are extensively used. These stokers are not so 
varied in design as those in the smaller classes although the principle is 
much the same. Practically all of them are of the front coal feed type, 
either power driven or steam driven. Dump plates at the side are 
manually operated. These stokers are heavily built and designed to 
operate continuously at high boiler ratings with a minimum amount of 
attention. Because of the fact that all volatile gases must pass through the 
fire before reaching the combustion chamber, these stokers will operate 
smokelessly under ordinary conditions. Also because of the fact that 
these stokers are always provided with forced draft, they are the most 
desirable type for fluctuating loads or high boiler ratings. 
' In the design of the grates for supporting the fuel between the retort 
and the ash plates, the stokers differ in providing for movement of the 
fuel during combustion. Some stokers are designed with fixed grates of 
sufficient angle to provide for this movement as the bed is agitated by the 
incoming fuel, while others have alternate moving and stationary bars in 
this area and provide for this movement mechanically. In either type, 
with 'proper operation, all refuse will be deposited at the dump plate. 

208 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

Recent developments in this type of stoker provide for sliding distributor 
blocks along the bottom of the retorts which give flexibility in providing 
proper distribution of fuel over the grate area and assist in preventing 
coke masses when strong coking coals are used. Another difference in 
these stokers is that some use a single air chamber under the whole grate 
area thus having the same air pressure under the ignition area as under 
the rest of the grate, while others have a divided air chamber using the 
full air pressure under the ignition area and a reduced air pressure under 
the remainder of the grate. These stokers vary in size from approxi- 
mately 5 sq ft to a maximum of 8% sq ft. 

The most prevalent type of rear cleaning underfeed stoker is the 
multiple retort design. Occasionally double or triple retort side cleaning 
underfeeds are made. The multiple retort underfeed stoker is made for 
the largest sizes of boilers for large industrial plants and central stations. 
This stoker has reached a very fine stage of development mechanically 
and in the matter of air supply and control. In some instances zoned air 
control has been applied both longitudinally and transversely to the grate 
surface. Ash dumps on smaller sizes are sometimes manually operated. 

The Combustion Process 

Due to the marked differences in design and operating characteristics 
of stokers and the widely differing characteristics of stoker fuels, it is 
difficult to generalize on the subject of combustion in automatic stokers. 

In anthracite stokers, which are almost exclusively of the small (Class 1) 
underfeed type, burning takes place within the stoker retort. The ash 
and refuse of combustion spills over the edge of the retort into an ashpit 
or receptacle from which it may be removed either manually or auto- 
matically. Anthracite is usually supplied for stoker firing in No. 1 
buckwheat or No. 2 buckwheat size. Those stokers burning coke operate 
in a similar manner to anthracite stokers. 

Since the majority of bituminous coal stokers used in heating plants 
operate on the underfeed principle some general observations of their 
operation are given. 

When the coal is fed from the hopper or bin into the retort it is generally 
degraded to some extent and some segregation of sizes occurs. Because 
of these factors there may be some difference in the actions occurring in the 
various portions of the retort. 

The coal moving upward in the retort toward the zone of combustion 
established by previous kindling of the fire is heated by conduction and 
radiation from the zone of combustion. As the temperature of the coal 
rises it first gives off moisture and occluded gases, which are largely 
non-combustible. When the temperature increases to around 700 or 
800 F, the coal particles become plastic, the degree of plasticity varying 
with the type of coal. 

A rapid evolution of combustible volatile matter occurs during and 
directly after the plastic stage of the coal. The distillation of volatile 
matter continues above the plastic zone and the coal is coked. The 
strength and porosity of the coke formed will vary according to the size 
and characteristics of the coal used. 

209 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

As more coal is fed from below the mass of coke continues to grow 
forming a coke tree, plug or spar as it is variously designated. After a 
period of time, dependent upon the strength of the coke formed, pieces of 
the coke tree break off and fall upon the hearth surrounding the retort 
or within the retort itself where they are burned. 

While part of the ash fuses into particles at the surface of the coke as it 
is released, most of it is freed in unfused flakes or grains. The greater 
part of this unfused ash remains on the hearth or dead plates although a 
part may be expelled from the furnace with the gases. 

The ash layer becomes thicker with time and that near the retort, being 
exposed to temperatures which are high enough at times, fuses into a 
clinker. The temperature attained in the fuel bed, the chemical compo- 
sition and homogeneity of the ash, and the time of heating are factors 
which govern the degree of fusion. 





FIG. 8. CROSS-SECTION OF FUEL BED 
WITH WEAKLY COKING COAL 



FIG. 9. CROSS-SECTION OF FUEL BED 
WITH STRONGLY COKING COAL 



Bituminous coal stokers of the Class 1 type operate on the principle 
of the removal of ash as clinker and clinker tongs are provided to facilitate 
this purpose. Typical representations of underfeed bituminous stoker 
fuel beds are shown in Figs. 8 and 9. 

The appearance of such fuel beds is very ragged at times, and large 
masses of coke build up, surrounded by blowholes with intense white 
flame indicating the presence of excess air. There is a natural tendency 
for users to disturb the fuel bed and make it conform to the conventional 
representation or ideal fuel bed. Such attention should not be required, 
as usually the fuel bed tends to correct its own faults as the cycles of 
plasticity, coke tree formation and ash fusion recur. 

There are a number of factors which materially affect the rate and type 
of ^ combustion obtained in stoker usage, the most important of these 
being: the type and design of stoker, the type and characteristics of the 
fuel, the method of stoker installation and the method of stoker operation. 

210 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 



Furnace Design 

The burning of the fuel on the grate or in the retort will be influenced 
directly by the stoker design. The burning of the volatile gases above the 
fuel bed is a matter of furnace design. Proper care should be taken to 
provide furnaces sufficiently liberal in volume and with the grates or 
retorts at a sufficient distance from the heating surface to permit proper 
combustion of the gases. Smoke and low efficiency will result if the 
furnace is too small to permit proper mixing of the gases and completion 
of combustion. 



TABLE 1. RECOMMENDED SETTING HEIGHTS FOR HEATING BOILERS 
EQUIPPED WITH MECHANICAL STOKERS'* 

FIREBOX BOIUCBS 



Actual Loadb 


2500 


5000 


7500 


10000 


12500 


15000 


20000 | 


25000 


30000 


A 18" 


18' 


20" 


20" 


22" 


22" 


24" ! 


24" 


24" 


B 


42" 


48" 


54" 


60" 


66" 


72" 


78" ; 


84" 


84" 



A Distance from bottom of Water Leg to floor. B m Distance from Crown Sheet to bottom of Water Leg. 

COMPACT WELDED BOILERS 



Actual Loadb 


2500 j 5000 i 


7500 


| 10000 ' 


12500 


15000 


20000 


25000 


30000 


A 


18" 


18" 


20" 


i 20" 


22" 


22" 


24" ' 24" 


24" 


B 


30" 


33" 1 

! 


36" 


: 42" j 


45" 


48" 54" 


60" 


60" 



A = Distance from bottom of Water Leg to floor. B = Distance from Crown Sheet to bottom of Water Leg. 

H. R. T. BOILEBS 



HP 


50 


75 | 100 


125 


150 


i 

175 i 200 i 225 


250 


1 

275 300 


A 


5'-0" 


5'-6" ! 6'-0" 


6'-6" 


7'-0" 


7'-0" ; 7'-6" 8'-0" 


8'-6" 


9'-0" 9'-0" 



A = Distance from bottom of shell to floor. 



Hp - Installed horsepower. 



In the case of the Firebox or Compact Welded type boilers the desired setting height can be obtained by 
combining A and B dimensions. The load ratings shown for this class of boilers are actual developed loads 
in square feet of equivalent cast-iron steam radiation and are not manufacturers' ratings. 

The setting heights given for H. R. T. boilers may be used for developed loads up to 50 per cent above 
normal rating. 

From Data prepared by the Midwest Stoker Association. 

bExpressed as steam radiation, 1 sq ft = 240 Btu. 

The standards that have been most universally adopted for the propor- 
tioning of furnaces for bituminous coal stokers are those of the Midwest 
Stoker Association and the Steel Heating Boiler Instittite. See Chapter 13. 

Table 1 gives recommended setting heights for heating boilers equipped 
with mechanical stokers using bituminous coal. 

Furnace volume is not an important item in anthracite stoker instal- 
lations. Due care should be exercised for both anthracite and bituminous 
stokers to prevent intense heat application on the metal surfaces of the 
combustion chamber. The installation of a baffle or adjustment in setting 
height of the stoker may be desirable in some cases. 

211 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

The prime essentials of good furnace design are: correct proportions, 
moderate combustion rate, adequate furnace volume and sufficient flame 
clearance. If these factors are properly compensated for and provision is 
made for the proper mixing of the gases bituminous coal stokers will 
operate smokelessly. In those stokers which are operated intermittently, 
however, some smoke may be produced during the off periods. 

Combustion Adjustments 

Satisfactory stoker performance may be secured by regulating the coal 
feed and the air supply so as to maintain, as nearly as possible, an ideal 
balance between the load demand and the heat liberated by the fuel. 
When the coal is consumed at about the same rate as that which it is fed 
this balance exists and uniform fuel bed conditions will be found. Under 
such conditions no manual attention to the fuel bed should be required 
other than the removal of clinker in those stokers which operate on this 
principle of ash removal. 

Since complete combustion is not obtained in stoker furnaces receiving 
only the air theoretically required, it is necessary, even under the best 
of conditions, to supply from 30 to 50 per cent excess air to obtain desired 
combustion results. Due to the variable characteristics of solid fuels in 
burning, consideration must be given to a number of factors which affect 
the maintenance of the combustion conditions wanted. 

The specified rate of coal feed of a stoker may vary due to changes in 
the bulk density of the coal dependent upon : (a) the size of coal, (6) dis- 
tribution of size in the coal, (c) segregation of coal in the stoker hopper, 
and (d) friability of the coal. 

The following factors may affect the rate of air supply: (a) changes in 
fuel bed conditions and resistance, (&) changes in furnace draft due to a 
variety of causes, i.e., changes in chimney draft because of weather 
changes, seasonal changes, back drafts, failure or inadequacy of auto- 
matic draft regulator, use of chimney for other purposes, possible stoppage 
of the chimney and changes in draft resistance of boiler due to partial 
stoppage of the flues, and (c) changes in air inlet adjustments to the fan. 

Many domestic bituminous stokers now incorporate some method of 
automatic control which compensates for changes in fuel bed resistance. 
Since a secondary source of air due to leakage is present in most installa- 
tions, the use of an automatic draft regulator to maintain the furnace 
draft at about 0.05 in. of water is desirable. This is quite important with 
intermittently operated stokers. Some fuel is burned by natural draft in 
the off periods, when fuel is not being fed, and it is essential that the 
burning in these periods be controlled. With excessive draft, due either 
to fan pressure or chimney pull, an increase in the discharge of soot and 
fly ash from the combustion chamber will result. 

Measurement of the Efficiency of Combustion 

As efficient combustion is based upon a certain percentage of excess air, 
it is possible to determine the results by analysis of the gases formed by 
the combustion process. An Orsat apparatus can be used to determine the 
percentage (by volume) of the carbon dioxide (C0 2 ), oxygen (0 2 ) and 

212 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

carbon monoxide (CO) in the flue gases. Due to variations in the fuel bed 
and rate of burning of stoker-fired .solid fuels it is not sufficient to analyze 
a grab sample. A continuous gas sample drawn at a constant rate through- 
out an operating period of reasonably long duration should be used. 
A COz reading of 12.5 to 14 per cent indicates that the excess air 
supplied is in the range of 30 to 50 per cent. The presence of CO indicates 
a loss due to improper mixing of the air and the gases of combustion; 
As an increase in excess air maintained during on periods will decrease the 
tendency toward smoke in the off periods of intermittently operated 
bituminous coal stokers, care should be taken that the delivery of air by 
the fan is great enough to avoid smoke. 

Controls 

The industry developed by stokers in Classes 1, 2, 3 and 4 has been due 
as much to the application of proper controls as to the stoker itself. This 
is especially true of Class 1 stokers because of their application to resi- 
dential heating, a field wherein the majority of owners and users are not 
familiar with control problems or stoker operation. 

The usual controls applied are as follows: 

a. Thermostats (plain and clock). 

b. Limit Controls (steam, vapor, vacuum, hot water, or air). 

c. Stack Temperature or Time Controls (for actuating fires periodically). 

d. Relay (for low voltage controls). 

e. Safety or Overload Cutout (for protection against overload). 
/. Low Water Cutout (steam, vapor and vacuum). 

DOMESTIC OIL BURNERS 

An oil burner is a mechanical device for producing heat automatically 
and safely from liquid fuels. This heat is produced in the furnace or fire- 
pot of hot water or steam boilers or warm air furnaces and is absorbed by 
the boiler, and thus made available for distribution to the house through 
the heating system. 

With oil, as with any kind of fuel, efficient heat production requires that 
all combustible matter in the fuel shall be completely consumed and that 
it shall be done with a minimum of excess air. The combustion of oil is a 
rather rapid chemical reaction. Excess air provides an over supply of 
oxygen so that all of the oil, composed of carbon and hydrogen, will be 
completely oxidized and thus produce all the heat possible. The use of 
unreasonable quantities of air in excess of theoretical combustion require- 
ments results in lowered efficiencies due to increased stack losses. Such 
losses, if not accompanied by unburned products of combustion (saturated 
and unsaturated hydrocarbons, hydrogen, etc.), may be offset somewhat 
by increasing the secondary heating surfaces of the heat absorbing 
medium, boiler or furnace. 

Oil is a highly concentrated fuel composed mainly of hydrogen and 
carbon. In its liquid form oil cannot burn. It must be converted into a 
gas or vapor by some means. If the excess air ^is to be kept within 
efficient limits it means that air must be supplied in carefully regulated 

213 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

quantities. The air and oil vapor must be vigorously mixed to get a 
rapid and complete chemical reaction. The better the mixing, the less 
excess air that will be needed. The combustion must take place in a 
space that maintains the temperatures high so the reaction will not be 
stopped before completion. When equipped with a means of igniting the 
oil and safety devices to guard against mishaps, the oil burner possesses 
all of the elements to be efficient and automatic. 

The number of combinations of the characteristic elements of domestic 
oil burners is rather large and accounts for the variety of burners found in 
actual practice. Domestic oil burners may be classified as follows: 

1. AIR SUPPLY FOR COMBUSTION 

a. Atmospheric by natural chimney draft. 

b. Mechanical electric-motor-driven fan or blower. 

c. Combination of (a) and (b) primary air supply by fan or blower and secondary 

air supply by natural chimney draft. 

2. METHOD OF OIL PREPARATION 

a. Vaporizing oil distills on hot surface or in hot cracking chamber. 

b. Atomizing oil broken up into minute globules. 

(1) Centrifugal by means of rotating cup or disc. 

(2) Pressure by means of forcing oil under pressure through a small 

nozzle or orifice. 

(3) Air or steam by high velocity air or steam jet in a special type of 

nozzle. 

(4) Combination air and pressure by air entrained with oil under pressure 

and forced through a nozzle. 

c. Combination of (a) and (b). 

3. TYPE OF FLAME 

a. Luminous a relatively bright flame. An orange-colored flame is usually best 

if no smoke is present. 
6. Non-luminous Bunsen-type flame (i.e., blue flame). 

4. METHODS OF IGNITION 

a. Electric. 

(1) Spark by transformer producing high-voltage sparks. Usually 

shielded to avoid radio interference. May take place continuously 
while the burner is operating or just at the beginning of operation. 

(2) Resistance by means of hot wires or plates. 

b. Gas. 

(1) Continuous pilot light of constant size. 

(2) Expanding size of pilot light expanded temporarily at the beginning 

of burner operation. 

c. Combination electric sparks light the gas and the gas flame ignites the oil. 

d. Manual by manually-operated gas torch for continuously operating burners. 

5. MANNER OF OPERATION 

a. On and off burner operates only a portion of the time (intermittent). 

b. High and low burner operates continuously but varies from a high to a low 

flame. 

c* Graduated busner operates continuously but flame is graduated according to 
needs by regulating both air and oil supply. 

214 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

A trade classification of oil burners consists of the following general 
types : (a) gun or pressure atomizing, (&) rotary and (c) pot or vaporizing. 

The gun type, illustrated in Fig. 10 is characterized by an air tube, 
usually horizontal, with oil supply pipe centrally located in the tube and 
arranged so that a spray of atomized oil is introduced and mixed in the 
combustion chamber with the air stream emerging from the air tube. A 
variety of patented shapes are employed at the end of the air tube to 
influence the direction and speed of the air and thus the effectiveness of 
the mixing process. 



-fU* BOX WIL 




FIG. 10. GUN TYPE PRESSURE ATOMIZING OIL BURNER 





FIG. 11. CENTER FLAME VERTICAL 
ROTARY BURNER 



FIG. 12. WALL FLAME VERTICAL 
ROTARY BURNER 



The most distinguishing feature of vertical rotary burners is the 
principle of flame application. These burners are of two general types; 
the center flame and wall flame. In the former type, (Fig. 11) the oil is 
atomized by being thrown from the rim of a revolving disc or cup and the 
flame burns in suspension with a characteristic yellow color. Combustion 
is supported by means of a bowl-shaped chamber or hearth. The wall 
flame burner (Fig. 12) differs in that combustion takes place in a ring of 

215 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

refractory material, which is placed around the hearth. These types of 
burners are further characterized by their installation within the ashpit of 
the boiler or furnace: 

The pot type burner (Fig. 13) can be identified by the presence of a 
metal structure, called a pot or retort, in which combustion takes place. 

When gun type (pressure atomizing) or horizontal rotary burners are 
used the combustion chamber is usually constructed of firebrick or other 
suitable refractory material, and is part of the installation procedure. 

The oil burners are operated by a small electric motor which pumps the 
oil and some or all of the air required. The smallest sizes can generally 
burn not much less than 1 gal of oil per hour. The grade of oil burned 
ranges from No. 1 to No. 4. No. 4 oil is the heaviest and most viscous of 
the various grades mentioned. An oil burner satisfactory for No. 4 oil 
can burn any of the lighter grades easily but an oil burner recommended 
for No.. 2 oil should never be supplied with the heavier grades. It has been 
found that while the heavier grades of oil have a smaller heat value per 




FIG. 13. POT TYPE VAPORIZING BURNER 



pound, they have, due to greater density, a larger heat value per gallon. 
The relative economy of the various grades must be based upon price and 
the amount of excess air required for clean and efficient combustion. 

Boiler-Burner Units 

Boilers and air conditioners especially designed for oil burners are 
available to the purchaser of this type of equipment. They are used for 
replacements as well as for new installations. This type of equipment 
usually has more heating surface than the older coal-burning designs. 
Flue proportions and gas travel have been changed with beneficial results. 
All problems of combustion chamber design, capacities, efficiencies, etc., 
have been solved. The selection of the proper size of unit should be a 
simple process. 

COMMERCIAL OIL BURNERS 

Liquid fuels are used for heating apartment buildings, hotels, public 
and office buildings, schools, churches, hospitals, department stores, as 
well as industrial plants of all kinds. Contrary to domestic heating, con- 
venience seldom is a dominating factor, the actual net cost of heat pro- 

216 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

duction usually controlling the selection of fuel. Some of the largest officfc 
buildings have been using oil for many years. Many department stores 
have found that floor space in basements and sub-basements can be used 
to better advantage for merchandising wares, and credit the heat pro- 
ducing department with this saving. 

Wherever possible, the boiler plant should be so arranged that either 
oil or solid fuel can be used at will, permitting the management to take 
advantage of changes in fuel costs if any occur. Each case should be 
considered solely in the light of local conditions and prices. 

Burners for commercial heating may be either large models of types 
used in domestic heating, or special types developed to meet the condi- 
tions imposed by the boilers involved. Generally speaking, such burners 
are of the mechanical or pressure atomizing types, the former using 
rotating cups producing a horizontal torch-like flame. (Fig. 14). As much 




FIG. 14. HORIZONTAL ROTATING-CUP OIL BURNER 

as 350 gal of oil per hour can be burned in these units, and frequently they 
are arranged in multiple on the boiler face, from two to five burners to 
each boiler. 

The larger installations are nearly always started with a^hand torch, 
and are manually controlled, but the useof automatic control is increasing, 
and completely automatic burners are now available to burn the twc 
heaviest grades of oil. Nearly all of the smaller installations, in schools, 
churches, apartment houses and the like, are fully automatic. 

Because of the viscosity of the heavier oils, it is customary to heat them 
before transferring by truck tank, It also has been common practice to 
preheat the oil between the storage tank and the burner, as an aid to 
movement of the oil as well as to atomization. This heating is accomplished 
by heat-transfer coils, using water or steam from the heating boiler, and 
heating the oil to within 30 deg of its flash point. 

Unlike the domestic burner, units for large commercial applications 
frequently consist of atomizing nozzles or cups mounted on the boiler 
front with the necessary air regulators, the pumps for handling the oil 

217 



HEATING VENTUJWING AIR CONDITIONING GUIDE 1938 

and the blowers for air supply being mounted in sets adjacent to the 
boilers. In such cases, one pump set can serve several burner units, and 
common prudence dictates the installation of spare or reserve pump sets. 
Pre-heaters and other essential auxiliary equipment also should be in- 
stalled in duplicate. 

Boiler Settings 

As the volume of space available for combustion is the determining 
factor in oil consumption, it is general practice to remove grates and 
extend the combustion chamber downward to include or even exceed the 
ashpit volume; in new installations the boiler should be raised to make 
added volume available. Approximately 1 cu ft of combustion volume 
should be provided for every developed boiler horsepower, and in this 
volume from 1.5 to 2 Ib of oil can properly be burned. This cor- 
responds to a maximum liberation of about 38,000 Btu per cubic foot per 
hour. There are indications that at times much higher fuel rates may be 
satisfactory. This in turn suggests that the value of 38,000 Btu per cubic 
foot per hour might be adjusted according to good engineering judgment. 
For best results, care should be taken to keep the gas velocity below 40 ft 
per second. Where checkerwork of brick is used to provide secondary air, 

food practice calls for about 1 sq in. of opening for each pound of oil 
red per hour. Such checkerwork is best adapted to flat flames, or to 
conical flames that can be spread over the floor of the combustion chamber. 
The proper bricking of a large or even medium sized boiler for oil firing is 
important and frequently it is advisable to consult an authority on this 
subject. The essential in combustion chamber design is to provide 
against flame impingement upon either metallic or fire brick surfaces. 
Manufacturers of oil burners usually have available detailed plans for 
adapting their burners to various types of boilers, and such information 
should be utilized. 

The Combustion Process 

Efficient combustion, as previously indicated, must produce a clean 
flame and must use relatively small excess of air, i.e., between 25 and 50 
per cent. This can be done only by vaporizing the oil quickly, completely, 
and mixing it vigorously with air in a combustion chamber hot enough 
to support the combustion. A vaporizing burner prepares the oil, for 
combustion, by transforming the liquid fuel to the gaseous state through 
the application of heat. This is accomplished before the oil vapor mixes 
with air to any extent and if the air and oil vapor temperatures are high 
and the fire pot hot, a clear blue flame is produced. There may be a 
deficiency of air as shown by the presence of carbon monoxide (CO) or 
an excessive supply of air, depending upon burner adjustment, without 
altering the clean, blue appearance of the flame. 

An atomizing burner i.e., gun and rotary types is so named because the 
oil is mechanically separated into very fine particles so that the surface 
exposure of the liquid to the radiant heat of the combustion chamber is 
vastly increased and vaporization proceeds quickly. The result of such 
practice is the ability to burn more and heavier oil within a given com- 
bustion space or furnace volume. Since the air enters the fire pot with the 
liquid fuel particles, it follows that mixing, vaporization and burning are 

218 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

all occurring at once in the same space. This produces a luminous 
instead of a blue or non-luminous flame. In this case a deficient amount 
of air is indicated by a dull red or dark orange flame with smoky flame tips. 

An excessive supply of air may produce a brilliant white flame in some 
cases or, in others, a short ragged flame with incandescent sparks flashing 
through the combustion space. While extreme cases may be easily 
detected, it is generally not possible to distinguish, by the eye alone, the 
finer adjustment which competent installation requires. 

Certain tests indicate that there is no difference in economy between a 
blue flame and a luminous flame if the position, shape and the per cent of 
excess air of both flames are about the same. 

Furnace or Combustion Chamber Design 

The furnace or combustion chamber may be defined as that part of a 
boiler or conditioner in which combustion is established. With burners 
requiring a refractory combustion chamber the size and shape should be in 
accordance with the manufacturer's instructions. It is important that 
the chamber shall be as nearly air tight as is possible, except when the 
particular burner requires a secondary supply of air for combustion. 

It is evident that the atomizing burner is dependent upon the surround- 
ing heated refractory or fire brick surfaces to vaporize the oil and support 
combustion. While the importance of the combustion chamber is obvious, 
its design has been troublesome. Unsatisfactory combustion may be due 
to inadequate atomization and mixing. A combustion chamber can only 
compensate for these things to a limited extent. If liquid fuel continually 
reaches some part of the fire brick surface, a carbon deposit will result. 
Fundamentally, the combustion chamber should enclose a space having a 
shape similar to the flame but large enough to avoid flame contact. 
The nearest approach in practice is to have the bottom of the combustion 
chamber flat but far enough below the nozzle to avoid flame contact, 
the sides tapering from the air tube at the same angle as the nozzle spray 
and the back wall rounded. A plan view of the combustion chamber thus 
resembles in shape the outline of the flame. In this way as much fire brick 
as possible is close to the flame so it may be kept quite hot. This insures 
quick vaporization, rapid combustion and better mixing by eliminating 
dead or inactive spaces in the combustion chamber. An overhanging 
arch at the back of the fire pot is sometimes used to increase the flame 
travel and give more time for mixing and burning and sometimes to pre- 
vent the gases from going too directly into the boiler flues. When good 
atomization and vigorous mixing are achieved by the burner, combustion 
chamber design becomes a less critical matter. Where secondary air is 
used, combustion chamber design is quite important. With some of the 
vertical rotary burners considerable care must be exercised in definitely 
following the manufacturers instructions when installing the hearth as 
in this class successful performance depends upon this factor. 

Combustion Adjustments 

Where adjustments of oil and air have been made which give efficient 
combustion, the problem of maintaining the adjustments constant be- 
comes an important one. Particularly is this true when the change 
causes" the per cent of excess air to decrease below allowable limits of the 

219 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

burner. A decrease in air supply while the oil delivery remains constant 
or an increase in oil delivery while the air supply remains constant will 
make the mixture of oil and air too rich for clean combustion. The more 
efficient the adjustment (i.e., 25 per cent excess air) the more critical it 
will be of variations. The oil and air supply rates must remain constant. 

The following factors may influence the oil delivery rate: (a) changes 
in oil viscosity due to temperature change or variations in grade of oil 
delivered, (6) erosion of atomizing nozzle, (c) fluctuations in by-pass relief 
pressures and (d) possible variations in methods 2b (3) and 2b (4) listed in 
the previous classification table. Note that any change due to partial 
stoppage of oil delivery will increase the proportion of excess air. This 
will result in less heat, reduced economy and possibly a complete inter- 
ruption of service but usually no soot will form. 

The following factors may influence the air supply: (a) changes in 
combustion draft due to a variety of causes (i.e., changes in chimney 
draft because of weather changes, seasonal changes, back drafts, failure 
or inadequacy of automatic draft regulator, use of chimney for other 
purposes, possible stoppage of the chimney and changes in draft resis- 
tance of boiler due to partial stoppage of the flues), and (6) changes in air 
inlet adjustments to the fan. 

It is recognized that a secondary source of air due to leakage in the 
boiler setting is present in many installations and it is highly desirable that 
this leakage be reduced to a minimum. Obviously the amount of air 
leakage will be determined by the draft in the combustion chamber. 
It is important that this draft should be reduced as low as is consistent 
with the proper disposal of the gases of combustion. When using mechani- 
cal draft burners with average conditions, the combustion chamber draft 
should not be allowed to exceed 0.02-0.05 in. water. An automatic draft 
regulator is very helpful in maintaining such values, 

Measurement of the Efficiency of Combustion. 

Efficient combustion being based upon a clean flame and certain 
proportions of oil and air employed, it is possible to determine the results 
by analyzing the gases formed by the combustion process. An Orsat 
apparatus is a device which measures the volume of carbon dioxide 
(C0 2 ), oxygen (0%) and carbon monoxide (CO) in the flue gases. Except 
in the case of a non-luminous flame it is usually sufficient to analyze only 
for carbon dioxide (CO*). A showing of 10 to 12 per cent indicates the 
best adjustment if the flame is clean. Most of the good installations at 
the present time show from 8 to 10 per cent COg. Taking into account 
the potential hazard of oil or air fluctuations with low excess air (high 
CO*) a setting to give 10 per cent COz constitutes a reasonable standard 
for most oil burners. This is particularly true of non-luminous flame 
burners which will not function properly with less than 10 per cent COa. 

Controls 

Oil burner controls may be divided into two parts: (a) devices to 
regulate burner operation so the desired house heating result may be 
obtained and (&) devices for the safety and protection of the boiler and 
burner. For control devices generally consult Chapter 37. The room 
thermostat has recently been improved to provide more frequent burner 

220 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

operation and greater uniformity' of room temperature. Class (b) controls 
comprises a device to shut off the burner if the oil fails to ignite or if the 
flame should cease due to lack of oil; a device actuated by steam boiler 
pressure to shut off the burner when the pressure reaches some pre- 
determined value; a device on the boiler to shut off the burner if the water 
level acts too low for safety or one which automatically feeds additional 
water to the boiler; a device on warm air furnaces to shut off the burner if 
the air temperature gets too high; a valve in the oil supply line which 
automatically closes in the event of fire in or near the cellar; and a device 
to keep the temperature of the boiler water within certain limits when it is 
being used to heat domestic hot water. These devices are all tested and 
approved by the Underwriters' Laboratory of Chicago, 111., before they 
are offered to the purchaser. The selection of class (&) devices is made by 
the oil burner manufacturer. 

Fuel Oil Gages 

To insure a constant supply of fuel oil and to check deliveries and 
consumption it is essential to have accurate means of readily determining 
the quantity of oil in the storage tank. For this purpose various types of 
indicating or recording gages are used, the simplest forms being the glass 
level gage, and a float-and-dial arrangement having a graduated dial face 
indicating the proportion of the tank containing liquid. Other more 
accurate and dependable devices are designed to operate by hydraulic 
action or by hydrostatic impulse. These instruments may be attached to 
the tank, giving a direct reading of the liquid contents; or the instrument 
itself may be located at a convenient point remote from the tank and 
connected with the tank by pipe or tubing. The quantity readings may 
be in gallons of liquid, height of liquid level in feet and inches, or in other 
desired units of measurement. 

GAS-FIRED APPLIANCES 

The increased use of gas for house heating purposes has resulted in the 
production of such a large number of different types of gas heating 
systems and appliances that today there is probably a greater variety of 
them than there is for any other kind of fuel. 

Gas-fired heating systems may be classified as follows : 

I. Gas-Designed Heating Systems. 

A. Central Heating Plants. 

1. Steam, hot water, and vapor boilers. 

2. Warm air furnaces. 

B. Unit Heating Systems. 

1. Warm air floor furnaces. 

2. Industrial unit heaters. 

3. Space heaters. 

4. Garage heaters. 

II. Conversion Heating Systems. 
A, Central Heating Plants. 

1. Steam, hot water and vapor boilers. 

2. Warm air basement furnaces. 

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HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

These systems are supplied with either automatic or manual control. 
Central heating plants, for example, whether gas designed or conversion 
systems, may be equipped with room temperature control, push-button 
control, or manual control. 

Gas-Fired Boilers 

Information on gas-fired boilers will be found in Chapter 13. Either 
snap action or throttling control is available for gas boiler operation. 
This is especially advantageous in straight steam systems because steam 
pressures can be maintained at desired points, while at the same time 
complete cut-off of gas is possible when the thermostat calls for it. 

Gas-Fired Warm Air Furnaces 

Warm air furnaces are variously constructed of cast iron, sheet metal 
and combinations of the two materials. If sheet metal is used, it must 
be of such a character that it will have the maximum resistance to the 
corrosive effect of the products of combustion. With some varieties of 
manufactured gases, this effect is quite pronounced. Warm air furnaces 
are obtainable in sizes from those sufficient to heat the largest residence 
down to sizes applicable to a single room. The practice of installing a 
number of separate furnaces to heat individual rooms is peculiar to mild 
climates. Small furnaces, frequently controlled by electrical valves 
actuated by push-buttons in the room above, are often installed to heat 
rooms where heat may be desired for an hour or so each day. These 
furnaces are used also for heating groups of rooms in larger residences. 
In a system of this type each furnace should supply a group of rooms in 
which the heating requirements for each room in the group are similar as 
far as the period of heating and temperature to be maintained are con- 
cerned. 

The same fundamental principle of design that is followed in the con- 
struction of boilers, that is, breaking the hot as into fine streams so that 
all particles are brought as close as possible to the heating surface, is 
equally applicable to the design of warm air furnaces. 

Codes for proportioning warm air heating plants, such as that formu- 
lated by the National Warm Air Heating and Air Conditioning Association 
are equally applicable to gas furnaces and coal furnaces. Recirculation 
should always be practiced with gas-fired warm air furnaces. It not only 
aids in heating, but is essential to economy. Where fans are used in con- 
nection with warm air furnaces for residence heating, it is well to have the 
control of the fan and of the gas so coordinated that there will be sufficient 
delay between the turning on of the gas and the starting of the fan to 
prevent blasts of cold air being blown into the heated rooms. An additional 
thermostat in the air duct easily may be arranged to accomplish this. 

Floor Furnaces 

Warm air floor furnaces are well adapted for heating first floors, or 
where heat is required in only one or two rooms. A number may be used 
to provide heat for the entire building where all rooms are on the ground 
floor, thus giving the heating system flexibility as any number of rooms 
may be heated without heating the others. With the usual type the 
register is installed in the floor, the heating element and gas piping being 

222 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

suspended below. Air is taken downward between the two sheets of the 
double casing and discharged upward over the heating surfaces and into 
the room. The appliance is controlled from the room to be heated by 
means of a control lever located near the edge of the register. The handle 
of the control is removable as a precaution against accidental turning 
on or off of the gas to the furnace. 

Space Heaters 

Space heaters are generally used for auxiliary heating, but may be, and 
are in many cases, installed for furnishing heat to entire buildings. With 
the exception of wall heaters, they are portable, and can be easily removed 
and stored during the summer season. Although they should be connected 
with solid piping it is sometimes desirable to connect them with flexible 
gas tubing in which case a gas shut-off on the heater is not permitted, and 
only A.G.A. approved tubing should be used. 

Parlor furnaces or circulators are usually constructed to resemble a 
cabinet radio. They heat the room entirely by convection, i.e., the cold 
air of the room is drawn in near the base and passes up inside the jacket 
around a drum or heating section, and out of the heater at or near the top. 
These heaters cause a continuous circulation of the air in the room during 
the time they are in operation. The burner or burners are located in the 
base at the bottom of an enclosed combustion chamber. The products of 
combustion pass up around baffles within the heating element or drum, 
and out the flue at the back near the top. They are well adapted not only 
for residence room heating but also for stores and offices. 

Radiant heaters^ make admirable auxiliary heating appliances to be used 
during the occasional cool days at the beginning and end of the heating 
season when heat is desired in some particular room for an hour or two. 
The radiant heater gives off a considerable portion of its heat in the form 
of radiant energy emitted by an incandescent refractory that is heated by 
a Bunsen flame. They are made in numerous shapes and designs and in 
sizes ranging from two to fourteen or more radiants. Some have sheet- 
iron bodies finished in enamel or brass while others have cast-iron or brass 
frames with heavy fire-clay bodies. An atmospheric burner is supported 
near the center of the base, usually by set screws at each end. Others 
have a group of small atmospheric burners supported on a manifold 
attached to the base. Most radiant heaters are supported on legs and are 
portable; however, there are also types which are encased in a jacket 
which fits into the wall with a grilled front, similar to the ordinary wall 
register. Others are encased in frames which fit into fireplaces. 

Gas-fired steam and hot water radiators are popular types of room heating 
appliances. They provide a form of heating apparatus for intermittently 
heated spaces such as stores, small churches and some types of offices and 
apartments. They are made in a large variety of shapes and sizes and are 
similar in appearance to the ordinary steam or hot water radiator con- 
nected to a basement boiler. A separate combustion chamber is provided 
in the base of each radiator and is usually fitted with a one-piece burner. 
They may be secured in either the vented or unvented types, and with 
steam pressure, thermostatic or room temperature controls. 

Warm air radiators are similar in appearance to the steam or hot water 
radiators. They are usually constructed of pressed steel or sheet metal 

223 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

hollow sections. The hot products of combustion circulate through the 
sections and are discharged out a flue or into the room, depending upon 
whether the radiator is of the vented or unvented type. 

Garage heaters are usually similar in construction to the cabinet 
circulator space heaters, except that safety screens are provided over all 
openings into the combustion chamber to prevent any possibility of 
explosion from gasoline fumes or other gases which might be ignited by 
an open flame. They are usually provided with automatic room tem- 
perature controls and are well suited for heating either residence or 
commercial garages, 

Conversion Burners 

Residence heating with gas through the use of conversion burners in- 
stalled in coal-designed boilers and furnaces represents a common type 
of gas-fired house heating system. In many conversion burners radiants 
or refractories are employed to convert some of the energy in the gas to 
radiant heat. Others are of the blast type, operating without refractories. 

Many conversion units are equipped with sheet metal secondary air 
ducts which are inserted through the ashpit door. The duct is equipped 
with automatic air controls which open when the burners are operating 
and close when the gas supply is turned off. This prevents a large part 
of the circulation of cold air through the combustion space of the ap- 
pliance when not in operation. By means of this duct the air necessary 
for proper combustion is supplied directly to the burner, thereby making 
it possible to reduce the amount of excess air passing through the com- 
bustion chamber. 

Conversion units are made in many sizes both round and rectangular 
to fit different types and makes of boilers and furnaces. They may be 
secured with manual, push-button, or room temperature control. 

The Combustion Process 

* Because of the varying composition of gases used for domestic heating 
it is difficult to generalize on the subject of gas burner combustion. 
Refer to the section on Gas Classification, in Chapter 9. 

Combustion Adjustments 

Little difficulty should be experienced in maintaining efficient com- 
bustion conditions when burning gas. The fuel supply is normally held 
to close limits of variation in pressure and calorific value and, therefore, 
the rate of heat supply is nominally constant. Since the force necessary to 
introduce the fuel into the combustion chamber is an inherent factor of 
the fuel, no draft by the chimney is required for this purpose. The use of a 
draft diverter insures the maintenance of constant low draft condition in 
the combustion chamber with a resultant stability of air supply. A draft 
diverter is also helpful in controlling the amount of excess air and pre- 
venting back drafts which might extinguish the flame. 

Measurement of the Efficiency of Combustion 

It is possible to determine the results of combustion by analyzing the 
gases of combustion with an Orsat apparatus. It is desirable to determine 

224 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 

the percentage of carbon dioxide (C0 2 ), oxygen (0 2 ) and carbon monoxide 
(CO) in the flue gases. While ultimate COz values of 10 to 12 per cent may 
be obtained from the combustion of gases commonly used for domestic 
heating, a combustion adjustment which will show from 8 to 10 per cent 
C0 a represents a practical value. Under normal conditions no CO will be 
produced by a gas-fired boiler or furnace. Limitations as to output rating 
by the A.G.A. are based upon operation with not more than 0.04 per cent 
CO in the products of combustion. This is too small an amount to be 
determined by the ordinary flue gas. analyzer. 

Controls 

Gas burner controls may be divided into two parts: (a) devices to 
regulate burner operation so that the desired house heating results may be 
obtained and (b) devices for the safety of the boiler and burner. Control 
devices are treated in detail in Chapter 37. A room thermostat may be 
used as a control of house heating effect. These may be obtained in a 
number of types. Some central heating plants are equipped with push- 
button or manual control. Class (&) controls include a device to shut off 
the burner if the gas fails to ignite, a device actuated by boiler pressure, 
water temperature, or furnace bonnet temperature to shut off the burner 
when the pressure or temperature becomes excessive, a device on the 
boiler to shut off the burner if the water level falls below safe limits or one 
which automatically feeds additional water to the boiler, and a device for 
controlling the gas pressure within desired limits. The main gas valve 
may be either of the snap action or throttling type. 

Sizing Gas-Fired Heating Plants 

While gas-burning equipment can be and usually is so installed as to be 
completely automatic, maintaining the temperature of rooms at a pre- 
determined and set figure, there are in use installations which are manually 
controlled. Experience has shown that, in order to effectively overcome 
the starting load and losses in piping, a manually-controlled gas boiler 
should have an output as much as 100 per cent greater than the equiva- 
lent standard cast-iron column radiation which it is expected to serve. 

Boilers under thermostatic control, however, are not subject to suclr 
severe pick-up or starting loads. Consequently, it is possible to use $ 
much lower selection, or safety factor. A gas-fired boiler under thermo 
static control is sensitive to variations in room temperatures so that ii 
most cases a factor of 20 per cent is sufficient for pick-up load. 

The factor to be allowed for loss of heat from piping, however, mus 
vary somewhat, the proportionate amount of piping installed being con 
siderably greater for small installations than for large ones. Consequent! 
a selection factor for thermostatically controlled boilers must be variable 
Liberal selection factors to be added to the installed steam radiatio 
under thermostatic control are given in Fig. 3 of Chapter 13. 

Appliances used for heating with gas should bear the approval seal < 
the American Gas Association Testing Laboratory. Installations shoul 
be made in accordance with the recommendations shown in the publ 
cations of that association. 

225 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

Ratings for Gas Appliances 

Since a gas appliance has a heat-generating capacity that can be pre- 
dicted accurately to within 1 or 2 per cent, and since this capacity is not 
affected by such things as condition of fuel bed and soot accumulation, 
makers of these appliances have an opportunity to rate their product in 
exact terms. Consequently all makers give their product an hourly Btu 
output rating. This is the amount of heat that is available at the outlet of 
a boiler in the form of steam or hot water, or at the bonnet of the furnace 
in the form of warm air. The output rating is in turn based upon the 
Btu input rating which has been approved by the American Gas Asso- 
ciation Testing Laboratory and upon an average efficiency which has 
been assigned by that association. 

In the case of boilers, the rating can be put in terms of square feet of 
equivalent direct radiation by dividing it by 240 foi steam, and 150 for 
water. This gives what is called the A merican Gas Association rating, and 
is the manner in which all appliances approved by the American Gas 
Association Laboratory are rated. To use these ratings it is only necessary 
to increase the calculated heat loss or the equivalent direct radiation load 
by an appropriate amount for starting and piping, and to select the boiler 
or furnace with the proper rating. 

The rating given by the American Gas Association Laboratory is not 
only a conservative rating when considered from the standpoint of 
capacity and efficiency, but is also a safe rating when considered from the 
standpoint of physical safety to the owner or caretaker. The rating that 
is placed upon an appliance is limited by the amount of gas that can be 
burned without the production of harmful amounts of carbon monoxide. 
This same limitation applies to all classes of gas-consuming heating 
appliances that are tested and approved by the Laboratory. Gas boilers 
are available with ratings up to 14,000 sq ft of steam, while furnaces with 
ratings up to about 500,000 Btu per hour are available. (See Chapter 20.) 

REFERENCES 

Stoker Information, Bulletin No. 5, Committee of Ten, 307 N. Michigan Ave., 
Chicago, III. 

Domestic Burners for Pennsylvania Anthracite, Commercial Standard CS48-34 
U. S. Department of Commerce. 

Performance Expectancy of Domestic Underfeed Stokers for Anthracite, by Allen J. 
Johnson (Transactions, A.I.M.E., Coal Division, Vol. 119, 1936). 

The Relation of the Size of Bituminous Coals to Their Performance on Small Under- 
feed Stokers The Relation of the Size in the Hopper to That Burned in the Retort, 
by R. A. Sherman and E. R. Kaiser, Technical Report No. 1, Bituminous Coal Research, 
Inc., (December, 1935) Pt. I. 

The Relation of the Size of Bituminous Coals to Their Performance on Small Under- 
feed Stokers Burning Tests on Four Typical Coals, by R. A. Sherman, E. R. Kaiser and 
H. R. Limbacher, Technical Report No. 1, Bituminous Coal Research, Inc. (July, 1937) 
Pt. II. 

Stoker Coals, Anonymous, Bulletin of Chesapeake and Ohio Railway Co., 1935. 

Study of Performance Characteristics of Oil Burners and Low Pressure Heating 
Boilers, by L. E. Seeley and E. J. Tavanlar (A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, 
p. 517). 

A Study of Intermittent Operation of Oil Burners, by L. E. Seeley and J. H. Powers 
(A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 317). 

226 



CHAPTER 11. AUTOMATIC FUEL BURNING EQUIPMENT 



Air Supply and Its Effect on Performance of Oil Burners and Heating Boilers, by 
L. E. Seeley," J. H. Powers and E. J. Tavanlar (A.S.H.V.E. TRANSACTIONS, Vol. 39, 1933, 
p. 7,5). 

Study of Fuel Burning Rates and Power Requirements of Oil Burners in Relation to 
Excess Air, by L. E. Seeley and E. J. Tavanlar (A.S.H.V.E. TRANSACTIONS, Vol. 40, 

1934, p. 319). 

Oil Burning in Residences, by D. W. Nelson (A.S.H.V.E. TRANSACTIONS, Vol. 41, 

1935, p. 355). 

Domestic Oil Burners, by A. H. Senner (Mechanical Engineering, November, 1936). 

A Study of Oil-Fired Heating Boilers, by R. C. Cross and \V. R. Lyman (Heating and 
Ventilating, October, 1931). 

Value of Oil Burner Installation Surveys, by R. C. Cross and W. R. Lyman (Heating 
and Ventilating, January, 1931). 

House Heating, Industrial Gas Series, American Gas Association. 

Approval Requirements of Central House Heating Gas Appliances, American Gas 
Association. 

A Method for Determining Fuel Burning Rates in Heating Boilers Fired by Auto- 
matic Devices, by R. C. Cross (Heating and Ventilating, January, 1932). 

Heat Losses and Efficiencies of Fuels in Residential Heating, by R. A. Sherman and 
R. C. Cross (A.S.H.V.E. JOURNAL SECTION, Heating, Piping and Air Conditioning, 
January, 1937, p. 53). 

Efficiencies and Costs of Various Fuels in Domestic Heating, by R. A. Sherman and 
R. C. Cross, Technical Report No. 3, Bituminous Coal Research, Inc., (December, 1936). 

Automatic Heating Equipment, American Architect Reference Data, No. 7, September, 
1933. 



PROBLEMS IN PRACTICE 

1 List some factors which might account for higher efficiencies with stoker 
firing than with hand firing. 

a. The uniform rate of coal feed, b. Better distribution in the fuel bed, and c. Positive 
control of the air supplied for combustion. 

2 Classify stokers as to construction and operation. 

a. Overfeed flat grate, b. Overfeed inclined grate, c. Underfeed side cleaning type, and 
d. Underfeed rear cleaning type. 

3 What classification may he made of stokers as to their use? 

Class 1. For residences (Capacity up to 60 Ib of coal per hour). 

Class 2. For apartment houses and small commercial heating plants (Capacity 60 to IOC 
Ib of coal per hour). 

Class 3. For medium sized commercial heating plants (Capacity 100 to 300 Ib of coa 
per hour). 

Class 4. For large commercial plants and small high pressure steam plants (Capacity 
300 to 1200 Ib of coal per hour). 

4 What main parts are found in an underfeed residential stoker? 

A hopper is supplied to hold coal which is fed by a screw or plunger into a retort provide 
with air openings called tuyeres. A blower supplies air under pressure for combustion, an 
a gear case provides for changes in coal feeding rates. 

5 What is a dead-plate? 

A dead-plate is a flat surface without air supply openings upon which the fuel rests whi 
combustion of the fixed carbon is completed. Generally the ash is removed from tl 
dead-plate. 

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HEATING VENTUJLTING AIR CONDITIONING GUIDE 1938 

6 What features of furnace design are essential for the proper burning of 
the volatile coal gases above the fuel bed? 

Adequate provisions should be made so that the furnace volume is sufficiently liberal 
and that the grates are a sufficient distance from the heating surfaces to permit the 
proper combustion of gases- 

7 What methods of oil atomization are used? 

a. Throwing the oil from a rotating cup or disc, b. Forcing the oil under high pressure 
through a nozzle, c. Propelling the oil with a high velocity jet of air or steam, and d. 
Forcing an oil and air mixture through a nozzle. 

8 What is the purpose of atomization? 

Atomization is used to increase the surface area of the oil in order to facilitate putting it 
into a vaporous state so it may burn. 

9 Is the furnace of much importance in oil burning? 

In most cases it is very important. It is the function of the oil burner to supply the air 
and fuel in correct proportions; the furnace must provide heated space for proper mixing 
and combustion. 

10 Which flame is considered better, the luminous or the non-luminous? 

Laboratory tests show that they are equally efficient in the usual installation. 

11 How should oil burner adjustments be made? 

Adjustments should be made by an experienced man who uses a gas analysis apparatus 
to determine the COz content. 

12 What CO 2 content should be attained in oil burning? 

Ten per cent CO t is considered good practice, for it indicates the supplying of 50 per cent 
excess air. 

13 What maximum heat release is considered good practice in oil burning? 

A heat release of 38,000 Btu per cubic foot per hour is considered to be the maximum for 
average large installations. This figure has been greatly exceeded in some cases. _The 
design of the combustion chamber, as to impingement of flame and as to proper mixing 
at high temperatures, has much to do with the attainable heat release. 

14 Name five types of gas-fired space heaters. 

a. Parlor furnaces or circulators. 

b. Radiant heaters. 

c. Gas-fired steam or hot water radiators. 

d. Warm air radiators. 
. Garage heaters. 

15 How are gas heating units rated? 

Gas-fired units are rated on the basis of output in Btu per hour. 

16 What safety consideration is noted in establishing the ratings of gas-fired 
units? 

The rating is limited by the amount of gas that can be burned without the liberation of 
harmful amounts of carbon monoxide. 



228 



Chapter 12 

HEAT AND FUEL UTILIZATION 

Total Heat Loss Requirements, Utilization Factors, Degree- 

Day Methods, Base Temperature Determinations, Steam 

Consumption of Buildings, Fuel Consumption, Maximum 

Demands, Load Factors 

/ HT V HE hourly heat loss (If) is equal to the sum of the transmission 

1 losses (fit) and the infiltration losses (Hi) of the rooms or spaces to 

be heated. The total equivalent heating surface required is equal to 



In estimating the fuel consumption of a building of more than one 
room divided by walls or partitions, it is not correct to use the calculated 
heat loss of the building without making the proper allowances for the 
fact that the heating load at any time does not involve the sum of the 
infiltration losses of all the heated spaces of the building but only part of 
the infiltration losses. This is explained in Chapter 6. 

It is sufficiently accurate in most cases to consider only half of the total 
infiltration losses of a building having interior walls and partitions. The 
value of H in Equation 1 would, under these conditions, be equal to 

Hi + -~. In some cases, where the building has no interior walls or 
2> 

partitions, the infiltration losses are calculated by using only half of the 
total crack. In this case the entire infiltration loss should be considered. 
The heat required to warm the cold building and contents is a factor to 
be considered. Under certain conditions the cooling of the structure and 
contents will, to some extent, compensate for the heat required to rewarm 
the building. For example, if the building is under thermostatic control 
and the day and night temperatures are, 70 F and 50 F respectively, there 
will be a period during which no heat will be added while the building is 
cooling to 50 F, and the saving resulting therefrom will correspond to the 
additional heat required to bring the building and contents back to the 
daytime temperature. 

ESTIMATING FUEL CONSUMPTION 

There are two methods in use for estimating heat or fuel consumption. 
One method is theoretical, based on a calculated heat loss and assuming 
absolute constant temperatures for very definite hours each day through- 
out the entire heating season. It does not take into account factors which 
are difficult to evaluate such as opening of windows, abnormal heating of 
the building, sun effect, poor heating systems, etc. 

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HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

The second method is based on steam consumption data which have 
been taken from a group of buildings in operation, and the results com- 
puted on a degree-day basis. While this method may not be as theo- 
retically correct as the first mentioned method, it is of more value for 
practical use. Calculations of heat consumption made by the second 
method will invariably be higher than calculations made by the first 
method. 

Theoretical Estimation Method 

To predict the amount of fuel likely to be consumed in heating a 
building during a normal heating season, it is necessary to know the total 
heat requirements of the building and the utilization factor of the fuel. 
The accuracy of the estimate will depend on the ability to select these 
values and on the care taken in making allowances for other variable 
factors. 

Heat requirements are given by the following general formula: 



Steam requirements are determined by dividing the above by 1000, 
thus: 



fa - to) 1000 
Fuel requirements may be determined by the following formula: 



(2) 



where 

t =s inside temperature, degrees Fahrenheit. 
id = inside design temperature, degrees Fahrenheit. 

/a = average outside temperature, degrees Fahrenheit (Table 2, Chapter 7). 
2o outside design temperature, degrees Fahrenheit. 

H = calculated heat loss of building based on outside temperature (/o), Btu per hour. 
N = number of heating hours per season; 5088 from October 1 to May I 1 . 
M = heat loss, Btu per season. 
5 = steam required to supply M Btu of heat loss. 
F = quantity of fuel required per heating season. 
C calorific value of one unit of fuel, the unit being the same as that on which 

F is based. 
E = efficiency of utilization of the fuel, per cent. 

Example 1. A small factory building located in Philadelphia is to be heated to 60 F 
between the hours of 7 A.M. and 7 P.M., and to 50 F during the remaining hours. The 
calculated hourly heat loss based on a design temperature of 6 F is 500,000 Btu. If 
coal having a calorific value of 12,500 Btu is fired and the overall heating efficiency is 
assumed to be 60 per_cent, how many pounds of steam would be required for a normal 
heating season? 

l This is the period for which t* (Table 2, Chapter 7) is calculated. If the heating season is different 
than this period, the corrected values may be substituted for N and t*. 

230 



CHAPTER 12. HEAT AND FUEL UTILIZATION 



Solution. Since there are no partitions in the building, the entire heat loss is con- 
sidered. From Table 2, Chapter 7, the average outside temperature ( 'fe) during the 
heating season is 42.7 F; N for the period for which fe. is taken (October 1 to May 1) is 
5088; H = 500,000; to -6 F; * = 50 F and 60 F; fo = 60 F; E = 00 per cent 
average for heating season; C - 12,500. 

The average daily temperature for the 24 hours is: 

50 X 12 + 60 _X 12 ^ 55 

Substituting in Equation 1: 

M = 500,000 X (55 - 42.7) X 5088 
60 -(-6) 

S = 474,100 Ib of steam. 

nor, 

.x- * 63,200 Ib of coal = 31.5 tons. 



Practical or Degree-Day Method 

The amount of heat required by a building depends upon the outdoor 
temperature, if other variables are eliminated. Theoretically it is pro- 
portional to the difference between the outdoor and indoor temperatures. 
Some^years ago the American Gas Association* determined from experi- 
ment in the heating of residences that the gas consumption varied directly 
as the difference between 65 F and the outside temperature. In other 
words, on a day when the temperature was 20 deg below 65 F, twice as 
much gas was consumed as on a day when the temperature was 10 deg 
below 65 F. The degree day is defined in Chapter 45. Degree-days for 
various cities in the United States and Canada are given in Table 1. 

Establishing the Base Inside Temperature. Recently the National 
District Heating Association has studied the metered steam consumption 
of 163 buildings 3 in 22 different cities and has published data substanti- 
ating the fact that the 65 F base originally chosen by the gas industry is 
approximately correct. 

The steam consumption of each building by months was divided by the 
number of days in each month, thus giving the average daily steam con- 
sumption by months. The average steam consumption was then plotted 
against the average monthly temperature, as shown in Fig, 1, and the 
temperature at which a line drawn through the points crossed the base 
line indicated the temperature corresponding to zero steam consumption, 
or the base temperature. The composite results from 163 buildings 
calculated in this manner are shown in Table 2. 

The resultant average of 66.0 F is close to the A.G.A. figure of 65 F. 
It will be noted that the base temperature calculated for hotels, apart- 
ments and residences is consistently higher than those for such buildings 
as garages, auto sales buildings, and manufacturing buildings. This, of 
course, would be expected in view of the higher inside temperatures 
carried in the former group; in fact, an even greater difference would be 



3 See Industrial Gas Series, House Heating (third edition) published by the American. Gas Association. 
'These buildings are all served with steam from a district heating company. 

231 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 1. DEGREE-DAYS FOR CITIES IN THE UNITED STATES AND CANADA* 



STATE , Cnr 


JAN. 


FEB. 


MAR. 


APR. 


MAY 


SEPT 


OCT. 


Nov 


DEC 


TOTAL 


Ala 
Ariz 
Ark 
Calif 
Col.. 


Birmingham 
Mobile 


. 589 
. 428 
.1153 
459 


577 
311 
969 
325 


260 
152 

i 896 
257 


69 








318 
186 
840 
252 


595 
394 
1128 
465 

"651 
301 
428 
1067 
1017 
1017 


2408 
1471 
7145 
1845 
2665 
2811 
1504 
3264 
6553 
5873 
5895 
4626 
890 
2891 
1490 
4558 
4924 
6315 
5370 
4164 
5297 
6373 
7023 
5034 
5301 
4616 
4180 
1023 
8531 
7012 
4533 
6045 
6464 
6494 
8692 
9480 
7851 
1822 
5202 
4585 
7115 
8699 
6231 
6128 
5891 
6852 
5175 
4934 
6063 
6889 
6821 
5348 
6785 
3234 
2302 
8498 






"577 


Flagstaff 
Tucson 

Hot Springs 


654 
87 


636b 


292d 


Little Rock 


719 
i 326 
! 465 
1085 
1079 
1110 


582 
266 
356 
993 
918 
1011 


353 
239 
354 
884 
799 
899 


78 
159 
294 
612 
534 
543 


"96" 
458b 
459b 
267 
223 


502c 
162 
72 
39 


47 

"146 
502 
428 
360 


381 
123 
261 
789 
759 
693 

"7S 
396 
201 
738 


Los Angeles._ 
San Francisco 
Colorado Springs.. 
Denver.- 


Conn.... 
D. C 


New Haven 
Washington 


Fla. 
Ga. 


Jacksonville 
Atlanta . 


285 
682 
409 
1098 


207 
558 
316 
848 


56 
388 
167 
651 


"m 


235" 


108"" 


""96 
*434 


267 
639 
397 
1011 


Idaho 


Savannah. 


Boise 


435 


III 


Lewiston 


Chicago 


1262 
1180 
949 
1128 
1392 
1434 
1116 
1221 
974 
939 
332 
1380 
1321 
955 
1150 


1095 
1008 
854 
969 
1173 
1386 
890 
980 
867 
801 
230 
232 
168 
843 
042 


909 
760 
640 
756 
890 
967 
688 
741 
648 
589 
58 
1110 
1017 
700 
908 


549 
365 
276 
384 
429 
489 
342 
339 
342 
264 

"786 
642 
348 
570 


248 
56 

"58" 
118 
164 
46 


30 
"33" 


353 
282 
155 
298 
357 
415 
276 
270 
245 
186 


756 
681 
528 
687 
798 
870 
672 
699 
612 
552 
102 
843 
780 
567 
693 

"777 
960 
062 
963 
252 
605 
597 
909 
041 


1113 
1038 
862 
1017 
1216 
1265 
1004 
1051 
903 
849 
301 
1228 
1153 
875 
1026 

lTl3 
1301 
1491 
1405 
471 
1038 
936 
192 
383 

"174 
974 
234 
893 
930 
073 
147 
104 
955 
140 
694 
527 


Ind 
Iowa 
Kans 
Ky 
La 


Springfield.- 
Evansville 
Indianapolis 
Des Moines._ 
Sioux City._ 
Dodge City 
Topeka 


Lexington 
Louisville.- 
New Orleans 


25 





Me._ 

Md 

Mass.. 


Eastport 
Portland 
Baltimore. 
Boston 


843b 
368 
22 
245 

226" 
682b 
22b 
35 


566^ 
120 


543 
443 
223 
363 

"5)0 
567 
620 
481 

"285 
205 
524 
620 

328 
452 
484 
254 
242 
459 
446 
418 
276 
426 
130 
19 


48 

~42~ 

268<i 
298d 
93 


Mich 
Minn 


Springfield 
Detroit. 
Marquette. 
Duluth 


1253 
1501 
1727 
1609 
520 
?01 


134 
360 
473 
400 
384 
987 
854 
120 
450 

125 
823 
240 
903 
942 
902 
142 
156 
960 
181 
630 
468 


976 
249 
277 
095 
195 
750 
657 
955 
168 

868 
753 
Oil 
806 
735 
775 
980 
032 
837 
991 
446 
322 


573 
804 
810 
570 


Miss 
Mo 


Minneapolis 
Vicksburg 


Kansas City 
St. Louis 
Billings 
Havre. 
Lincoln 
Omaha 
Reno 


321 
276 
534 
630 

414 
534 
669 
519 
402 
543 
549 
675 
486 
587 
183 
108 


15 

76b 
13 

84*" 
56b 
Sib 
20 
81 
Olb 
93 
47 
55 
44 




Mont 
Nebr 

Nev. 


1060 
1316 
1624 

1355 
1041 
1349 
992 
014 
110 
286 
240 
061 
242 
722 
555 




89 
70 

S" 
68 

20" 

72 
75 

87" 


780 
714 
846 
588 
588 
780 
774 
774 
618 
787 
429 
303 


N. H 


Concord 


N. J _ 


Atlantic City 


N. M 
N. Y 

N. C 

NT. Dak 


Trenton 
Santa Fe 
Albany. 
Buffalo 
New York 
Utica 
Raleigh 
Wilmington 
Bismarck. 













Heating and Ventilating Degree-Day Handbook. 
o Including June. 



clncluding July and August, 
d Including August. 



232 



CHAPTER 12. HEAT AND FUEL UTILIZATION 



TABLE 1. DEGREE-DAYS FOR CITIES IN THE UNITED STATES AND CANADA* (Continued) 



STATE 


Crrr 


JAN. 


FEB. 


MAE. 


APR. 


MAT 


SlPT. 


OCT. 


Nov. 


DEC. 


TOTAL 


Ohio 

Okla 

Oree. 


Cincinnati 
Cleveland 
Columbus 

Oklahoma City. 
Portland 


1076 
1180 
1113 
865 
806 


910 
1075 
980 
742 
644 


747 
950 
703 
465 
558 


378 
564 
420 
162 
402 


73 
220 
87 

335~b 


Tf 
165" 


290 
366 
313 
105 
332 


675 
732 
690 
459 
558 


980 
1060 
1017 
815 
728 


5129 
6154 
5323 
3613 
4468 
4629 
4855 
5235 
6014 
1769 
3257 
7683 
2950 
3578 
1578 
2455 
1157 
1202 
6735 
5553 
7620 
4243 
3349 
3725 
4968 
6353 
5016 
4884 
7612 
7823 
7290 
7372 
7462 


v & 
Pa 
R. I 

g^ 

S. Dak 
Tenn 

Texas 

Utah 

Vt... 
Va 

Wash 
W. Va 
Wis 

Wyo 


Salem. 


Philadelphia 
Pittsburgh. 
Providence. 
Charleston. 
Spartanburg 
Sioux Falls 
Memphis 
Nashville _ 
Austin 


1001 
1054 
1116 
487 
725 

"744 
812 


895 
944 
1069 
372 
688 

"599 
747 


756 
787 
890 
242 
431 

"384 
476 


402 
423 
558 
36 
147 

""96 
180 


68 
78 
251 


"63" 


242 
313 

54o 

"iTl" 
_ 

136 


588 
669 
693 
207 
429 

"402 
483 


903 
967 
1026 
425 
716 

"663 
744 

"335 
347 
1218 
1020 
1286 
878 
685 
765 
716 
1057 
977 

1328 
1322 
1280 
1222 
1143 




Dallas 
Houston 
San Antonio 
Logan ... 
Salt Lake City....!! 
Burlington 
Fredericksburg 
Norfolk 


Io6 
381 
1260 
1110 
1535 
887 
738 
825 
775 
1171 
1026 

1507 
1538 
1535 
1383 
1215 


"277 
274 
1072 
885 
1294 
820 
650 
702 
653 
952 
944 

1321 
1358 
1265 
1328 
1075 


"~65 
74 
893 
722 
1089 
583 
520 
552 
623 
778 
713 

1046 
1125 
1032 
1023 
995 





376" 
234 
276b 




"468 
388 
481 
223 
99 
158 
403 
514 
294 

"493 
505 
462 
449 
605 


Tl4 
126 
819 
723 
861 
549 
411 
483 
570 
819 
648 

"921 
921 
909 
846 
900 




~iiT 

18 
144 


525 
453 
654 
303 
246 
240 
465 
504 
414 

"603 
600 
528 
648 
720 


Richmond 
Seattle 
Spokane. 
Morgantown 
Parkersburg 
Fond du Lac. 
Green Bay. 
LaCrosse 


487b 
366 

276" 
322 
183 
389*> 
569 


276= 
192 

117" 
132 
96 
84 
240 


Milwaukee. 
Cheyenne. 



PROVINCE 


Cm 


JAN. 


FEB. 


MAE. 


APR. 


MAT 


SEPT. 


OCT. 


Nov. 


Die. 


TOTAL 


B. C. 


Victoria 




















5777 


Alb 


Vancouver. 
Kamloops 

Medicine Hat._ 





























5976 
6724 
8152 


Sask 
Man 


Qu'Appelle. 
Winnipeg- 





























11,261 
11,166 


Ont 


Port Arthur. 
Toronto -... . 





























10,803 

7732 


Que 

N. B 
N. S 
P. E. I..... 


Montreal 
Quebec 
Fredericton 
Yarmouth 

Charlottetown 


1615 


1409 


1219 


720 


309 


190 


372 


961 


1422 


8417 
8628 
9099 

7694 
8485 



aHeating and Ventilating Degree-Day Handbook. 
^Including June, 
elududing July and August. 



233 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 2. BASE TEMPERATURE FOR THE DEGREE-DAY** 



TTPI or BUILDING 


No. OF BUILDINGS 
ANALYZED 


TEMPERATURE F COR- 
RESPONDS TO ZERO 
STEAM CONSUMPTION 


Office 


60 
4 
3 
2 
6 
11 
12 
7 
14 
S 
4 
5 
3 
2 
2 
4 
3 
3 
2 
8 


66.2 
65.8 
66.2 
65.5 
67.4 
64.0 
64.3 
66.5 
68.8 
66.9 
65.5 
64.9 
67.6 
65.8 
64.8 
61.2 
67.7 
67.7 
65.2 
65.4 


Office and Bank. 


Bank 


Office and Telephone Exchange 
Office and Stores 


Stores. ._ . 


Department Stores 


Hotels........ . ..._. 


Apartments. _ 


Residences. 


Clubs 


Lodges _ 


Theatres... 


Churches. 


Garage. 
Auto Sales and Service. 

Newspaper and Printing 


Warehouse and Loft 


Office and Loft. 
Manufacturing 


Average for 163 Buildings 


66. OF 




Report of Commercial Relations Committee, 19S Proceedings, National District Heating Association. 



TABLE 3. STEAM CONSUMPTION FOR VARIOUS CLASSES OF BuiLDiNGs a 
(Heating Season Only) 



BUILDING CLASSIFICATION 


No. OF 
BUILDINGS 


STEAM CONSUMPTION 
POUNDS PER DEGREE-DAT 65 F BASIS* 


Per M Cu Ft 
of Heated 
Space 


Per M Sq Ft 
of Radiatorc 
Surface 


PerMBto 
perHrof 
HeatLossb 


Apartments 


16 
10 
12 
7 
10 
18 
6 
16 
7 
8 
6 
14 
6 
35 
35 


1.78 
1.46 
1.32 
1.25 
0.96 
0.90 
0.90 
0.89 
0.88 
0.83 
0.58 
0.57 
0.42 
1.09 
0.975 


97.5 

80.6 
64.2 
105.5 
77.0 
80.6 
75.0 
72.3 
45.2 
62.2 
49.4 
60.7 
72.3 
70.0 
65.4 


0.359 
0.371 


Hotels 


Residences 
Printing 

Clubs and Lodges. 


Retail Stores 

Theatres. .. 


0.268 
0.498 
0.283 


Loft and Mfg _ 


Banks 


Auto Sales and Service 


Churches 


67238 


Department Stores. 

Garages (Storage) 6 . _ 


Offices (Total) . 


0.283 
0.256 


Offices (Heating only) 



Includes steam for heating domestic water for heating season only. 

BHeat loss calculated for maximum design condition (in most cases 70 F inside, zero outside). 

cEquivalent steam radiator surface. 

dThe figures are a numerical not a -weighted average for the several buildings in each class. 

"Based on zero consumption at 55 F. 



234 



CHAPTER 12. HEAT AND FUEL UTILIZATION 



expected. For an average figure, the A .G.A . base of 65 F may therefore be 
safely used, and if greater refinement is desired, the figure for the type of 
building under consideration can be taken from Table 2. 

Table 3 4 gives the steam consumption per degree-day, expressed in 
three different ways, for 196 buildings in 14 different classifications. 
These buildings are divided among 21 different cities in the United States. 
The steam used for heating the domestic water is included in these 
figures, but in the case of office buildings, the steam for heating only is 
also shown. The data are placed on a comparable basis by expressing 
the steam consumption in terms of pounds per degree-day per thousand 
square feet of equivalent installed radiator surface, per thousand cubic 
feet of heated space, and per thousand Btu of calculated heat loss. 



3 PER DAY 




<? 


V 












\ 








3 

X 






^ 


^ 












\ 






STEAM CONSl 








\ 


\ 












\ 




AVERAGE ! 










\ 


^ 












\ 



AVERAGE TEMPERATURE FOR MONTH DEG F 

FIG. 1. METHOD OF DETERMINING BASE TEMPERATURE FOR 
DEGREE-DAY CALCULATIONS 6 

The choice of these units of comparison require some explanation. 
The use of heated space in preference to the gross cubage used by architects 
is obviously more accurate for this purpose. The architect's cubage 
includes the outer walls and certain percentages of attic and basement 
space which are usually unheated. The net heated space is usually about 
80 per cent of the gross cubage and can be calculated from the latter if it 
cannot be measured. The cubical content is somewhat inaccurate as a 
basis of comparison due to differences in types of construction, exposure, 
and ratio of exposed area to cubical contents. 

The use of radiator surface as the basis of comparison has two ob- 
jections. One is that the amount of radiator surface in a building is often 
either excessive or deficient, and figures for steam consumption based on 
it are therefore likely to be in error. Another reason is that it is difficult 
to convert fan coil surface into equivalent direct radiator surface with 
accuracy. On the whole, the use of radiator surface as the basis of com- 
parison is the least satisfactory of the three methods. 



*The Heat Requirements of Buildings, by J. H. Walker and G. H. Tuttle (A.S.H.V.E. TRANSACTIONS, 
Vol. 41, 1935, p. 171). 

Report of Commercial Relations Committee, 198& Proceedings, National District Seating Association. 

235 



HEATING VENTILATING Am CONDITIONING GUIDE 1938 

It should be noted that the figures in Table 3 are for the heating season 
only and include steam for heating domestic water. 

Example 1 solved by the degree-day method and using values taken 
from Table 3 would show a higher steam consumption. 

Example 8. Factor for steam consumption for a manufacturing building per M Btu 
per hour heat loss per degree-day - 0.283; total number of degree-days per year (Table 1) 
- 4855; heat loss = 500,000 Btu per hour. 

Solution. 0.283 X 4855 X 500 - 686,982 Ib of steam per year. This calculation 
results in an estimate 45 per cent higher than the previous calculation and one which 
would be more nearly correct for actual practice. 



TOO 



600 



500 



J400 



5300 



200 



100 




120 



100 



80 



O 



20 



I 234567B9 

STEAM CONSUMPTION - MILLION LB 

FIG. 2. CURVE FOR ESTIMATING FUEL CONSUMPTION FOR VARIOUS 
KNOWN STEAM CONSUMPTION* 

This curve is based on heating efficiencies of 60 to 70 per cent for coal and oil, respectively, a calorific 
value of coal of 13,000 Btu per pound, a calorific value of oil of 140,000 Btu per gallon. 

In case the heat loss figure is not known this method of estimating heat 
or steam consumption can also be applied if the net heated space figure 
is available. 



CALCULATION OF FUEL CONSUMPTION 

After the heat and steam consumption of the building have been calcu- 
lated, ^ the corresponding fuel requirements may also be estimated by 
assuming the correct boiler and furnace efficiencies. If the building is to 
be supplied with steam from a district heating company, the steam con- 
sumptions as calculated by the two Methods are generally assumed to be 
correct. However, if the steam is to be supplied from an individual boiler 

236 



CHAPTER 12. HEAT AND FUEL UTILIZATION 



unit, the consumption should be assumed as from 10 to 20 per cent greater. 
One reason for this difference in steam consumption is that district steam 
is a metered^ service, and building managers are therefore more conscious 
of their heating costs, which generally results in better maintained heating 
systems. Also, the district steam service is usually installed with ther- 
mostatic control which reduces overheating to a minimum. 

Fig. 2 shows the amount of coal or oil that may be estimated when the 
steam consumption is known. Assuming the steam consumption that 



1.4 



\ 



1.2 



1-Cu ft of gas per sq ft installed 

hot water radiation 
2-Cu ft of gas per sq ft installed 

steam radiation 
3- Cu ft of gas per 100 cu ft bldg 

contents hot air system 
4- Cu ft of gas per 1,000 Btu hourly 
loss from bldg. hot air system 




200 



500 600 700 
Btu VALUE OF GAS 



800 



900 1,000 1,100 



FIG. 3. CHART GIVING GAS REQUIREMENTS PER DEGREE-DAY FOR VARIOUS CALORIFIC 
VALUES OF GAS AND FOR DIFFERENT HEATING SYSTEMS* 

aTbis chart is based on an inside temperature of 70 F and an outside temperature of zero. If the radia- 
tion is installed on the basis of any other temperature difference, multiply the result obtained from this 
chart by 70, and divide by the actual temperature difference. From Industrial Gas Series House Heating, 
(third edition) published by the A merican Gas Association. 

was calculated in Example 2, 686,982 Ib, the corresponding coal con- 
sumption, from the curve, is 44 tons and the oil consumption 6000 gal. 

Fig. 3 indicates the average gas consumption per degree-day for 
various heat contents. While the fuel consumption in individual cases 
may vary somewhat from the curve values, these average values are 
sufficiently accurate for estimating purposes and give satisfactory results. 

The value generally used in the manufactured gas industry for resi- 
dences is 0.21 cu ft per degree-day per square foot of equivalent steam 
radiation (240 Btu) based on the theoretical requirements. A correction 
for warmer climates is necessary and it is customary to gradually increase 
the relative fuel consumption below 3000 degree-days to about 20 per cent 
more at 1000 degree-days. 

237 



g 
*l 
- Si 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



CALORIFIC VALUE OF FUEL 
J BTU PERLS -AS FIRED 






,0-1 K>- 



I I 




100 ' 20O 300 

GROSS OUTPUT -THOUSAND BT.U PER HOUR 



46 8 10 12 14 

GROSS OUTPUT- HUNDRED FEET STEAM RADIATION 



5 10 15 20 25 

GROSS OUTPUT - HUNDRED FEET WATER RADIATION 



FIG. 4. COAL FUEL BURNING RATE CHART. 



I 2 

SB* 

H* 
*!' 



100 200 300 

GROSS OUTPUT-THOUSAND BTU PER HOUR 




400 



500 



i 1 1 1 1 1 1 1 1 1 1 1 

4 6 8 10 12 14 

GROSS OUTPUT- HUNDRED FEET STEA'M RADIATION 



i i i 1 

18 20 



5 10 15 -20 25 30 

GROSS OUTPUT- HUNDRED FEET WATER RADIATION 
FIG. 5. OIL FUEL BURNING RATE CHARTS 

nil !l b j?o2 art S-kf 8 ^ upon No : 3 9 a Caving a heat content of 143,400 Btu per gallon. If other grades of 
2l^2n^i I ?S?9 l| fe o e ^fe ?%f ined from this chart b y the following factors: No. 1 oil (139,000 ^Btu 

SdfffiSawSi 4i?D^n? 25 S ffi^WJSSi 5?,; lilflttKPnSS 11 per **> a " 2 No - 



238 



CHAPTER 12. HEAT AND FUEL UTILIZATION 



For hot water or warm air heat the fuel consumption is about 0.19 cu ft 
per degree-day per square foot of equivalent steam radiation, that is, per 
240 Btu per hour. The actual requirements likewise relatively increase 
with hot water or warm air systems as the number of degree-days decreases 
below 3000. For larger installations, that is 1000 sq ft of theoretical 
radiation and above, there is an increase in efficiency, and a consequent 
decrease in the fuel consumption per degree-day per square foot of 
heating surface. 

The approximate quantities of steam required in New York City per 
square foot of heating surface for various classes of buildings are given in 
Chapter 42. 

The preceding discussion on fuel consumption has dealt with the 
heating requirements of the building irrespective of any air that may be 



GROSS CALORIFIC VALUE 
O O BT.U PER CUBIC FOOT 

CO O 



800- 500- 



300- 



200- 



200- 



100- 



300 



100 




. L 



100 200 300 

GROSS OUTPUT -THOUSAND &T.UL PER HOUR 



500 



4 6 8 10 12 14 

GROSS OUTPUT- HUNDRED FEET STEAM RADIATION 



05 IO 15 20 25 30 

GROSS OUTPUT - HUNDRED FEET WATER RADIATION 

FIG. 6. GAS FUEL BURNING RATE CHART. 

introduced for ventilation purposes other than the normal infiltration of 
outside air. The heat required for warming air brought into the building 
for ventilation may be estimated from data given in Chapters 3 and 21. 

Rate of Fuel Burning 

If the estimated maximum load or gross output is determined as out- 
lined in Chapter 13, the fuel burning rates for coal, oil, or gas may be 
determined from the charts illustrated in Figs. 4, 5 and 6. For a given 
efficiency, the rate of fuel burning is directly proportional to the gross 
output, and therefore, these charts can be extended by moving the 
decimal point the same number of digits in both vertical and horizontal 
scale. All charts are based upon values of one square foot steam radiation 
equivalent to 240 Btu per hour and one square foot hot water radiation 
equivalent to 150 Btu per hour. In using these charts, consideration 

239 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



must be given to the overall efficiency of the boiler or firing device. This 
factor is largely dependent upon good judgment and is a measure of the 
degree of efficiency to be expected from a particular installation. 

The correct fuel burning rate can be determined directly from the 
several charts for oil or gas burning installations, as these customarily 
operate on a strictly intermittent basis. These fuel burning devices 
usually introduce the fuel at a single fixed rate during the on periods and 
this rate should be sufficient to carry the gross or maximum design load. 
In the case of coal stokers, which are usually capable of variable rates of 
firing, it is desirable to operate at as low a rate as weather conditions will 
permit, but the maximum firing rate of the stoker should be sufficient 
to carry the gross load. This rate may be determined by the same method 
as used for oil or gas. 

In the case of warm air heating installations the heat loss of the building 
expressed in Btu per hour can be determined by use of the Standard 
Codes 6 of the National Warm Air Heating and Air Conditioning Asso- 
ciation. If the design heat loss of the building is divided by the proper 
factor, the required gross output may be obtained from the proper charts 
shown in Figs. 4, 5 and 6. 

Example 8.^ The estimated net load (including domestic hot water supply) as calcu- 
lated for a residence is 1500 sq ft of hot water radiation. Determine the firing rates for 
various fuels assuming an overall efficiency of 70 per cent ; using coal with a calorific value 
of 12,500 Btu per pound; No. 3 fuel oil and natural gas having a gross heating value of 
1000 Btu per cubic foot. 

Solution. Referring to Fig. 3, Chapter 13, a piping and pick-up factor for a net load of 
1500 sq ft is found to be 43 per cent or the gross output is equivalent to 1500 X 1.43 = 
2145 sq ft hot water radiation. 

Using the chart in Figs. 4, 5 and 6 project vertically from the gross output value on 
the proper horizontal scale to the intersection of the 70 per cent efficiency line. From the 
intersection of this line proceed horizontally to the proper vertical scale where a direct 
value of the required fuel burning rate is given. These values are rates of burning while 
firing device is in operation and are not indicative of hourly fuel consumption. 

By use of the respective charts the firing rates for the various fuels will be found to be: 
coal 36.8 Ib per hour, oil 3.2 gal per hour, and gas 460 cu ft per hour. 

TABLE 4. BUILDING LOAD FACTORS AND DEMANDS OF SOME DETROIT BUILDINGS'* 



BUILDING CLASSIFICATION 


LOAD FACTOR 


LB or DEMAND PER HR 
PER SQ FT OF EQUIVALENT 
INSTALLED RADIATOR SURFACE 


Clubs and Lodges 


318 


184 


Hotels 


316 


907 


Printing 


287 


217 


Offices 


263 


209 


Apartments 


255 


2^5 


Retail Stores 


238 


182 


Auto Sales and Service. 


0.223 


248 


Banks 


203 


158 


Churches. 


158 


152 


Department Stores 


0.138 


145 


Theatres 


126 


0151 









>Loc. Cit. Note 5. 



8 P% Installation of Gravity Warm Air Heating Systems in Residences 

edition) and the. Technical Code for the Design and Installation of Mechanical Warm Air Heating 
systems, may be obtained from the National Warm Air Heating and Air Conditioning Association, 50 W. 
Broad St., Columbus, Ohio. 

240 



CHAPTER 12. HEAT AND FUEL UTILIZATION 



MAXIMUM DEMANDS AND LOAD FACTORS 

In one form of district heating rates, a portion of the charge is based 
upon the maximum demand of the building. The maximum demand may 
be measured in several different ways. It may be taken as the instan- 
taneous peak or as the rate of use during any specified interval. One 
method is to take the average of the three highest hours during the 
winter. These figures are available for a number of buildings in Detroit, 
as shown in Table 4. 

These maximum demands were measured by an attachment on the 
condensation meter and therefore represent the amounts of condensation 
passed through the meter in the highest hours, rather than the true rate 
at which steam is supplied. There might be slight differences in these 
two quantities due to time lag and to storage of condensate in the system, 
but wherever this has been investigated it has been found to be negligible. 

The load factor of a building is the ratio of the average load to the 
maximum load and is an index of the utilization habits. Thus, in Table 4, 
the theatres, operating for short hours, have a load factor of 0.126 as 
compared with the figure of 0.318 for clubs and lodges. 



PROBLEMS IN PRACTICE 

1 What will be the cost per year of heating a building with gas, assuming that 
the calculated hourly heat loss is 92,000 Btu based on F, which includes 
26,000 Btu for infiltration? The design temperatures are F and 72 F. The 
normal heating season is 210 days, and the average outside temperature during 
the heating season is 36.4 F. The heating efficiency will be 75 per cent. The 
heating plant will be thermostatically controlled, and a temperature of 55 F 
will be maintained from 11 p.m. to 7 a.m. Assume that the price of gas is 
7 cents per 100,000 Btu of fuel consumption, and disregard the loss of heat 
through open windows and doors. 

The average hourly temperature is 

fc , (72 X 16) + (55 X 8) _ ^ p 

The maximum hourly heat loss will be 
H - 92,000 - 



79,000 (66.3 - 36.4) X 24 X 210 00 . . ,,,,,,,. , Dj . 

= 22046 hundred thousand Btu ' 



100.000 X 0.75 X (72-0) 
2204.6 X 0.07 = $154.34 = cost per year of heating the building. 

2 What factors should be taken into consideration when determining the 
efficiency at which a fuel will be burned? 

Manufacturers' catalogs usually give equipment efficiencies obtained under test con- 
ditions. These values do not allow for poor attendance, defects in installation, or poor 
draft. Such efficiencies do not consider heat radiated from the outside of the equipment, 
but in many cases this heat is utilized. 

241 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

3 If 20 tons of coal having a calorific value of 13,000 Btu per pound are burned 
in a warm air furnace and produce 236,000,000 Btu at the bonnet, what is the 
efficiency of the furnace? 

_ Number of Btu at bonnet _ _ ffi . 
Number of tons X calorific value X number of pounds in one ton ~~ e Clenc y- 

286,000,000 X 100 _ 
20 X 13,000 X 2000 " 65 per cent - 

4 Make a rough approximation of the gas required to heat a building located 
in Chicago, 111., assuming that the calculated heating surface requirements 
are 1000 sq ft of hot water radiation based on design temperatures of F and 
70 F. Chicago has 800-Btu mixed gas, and 6315 degree-days. 

Using Fig. 3, the fuel consumption for a design temperature of F with 800-Btu gas is 
found to be 0.08 cu ft of gas per degree-day per square foot of hot water radiation. 

0.08 X 6315 X 1000 = 505,200 cu ft. 

5 A certain building has a maximum heat loss of 250,000 Btu per hour in 15 F 
weather. How many tons of fuel will be required to maintain a temperature of 
70 F during a 260-day heating season in which the average temperature is 39 F? 
The heating value of the fuel is 13,200 Btu per pound and the efficiency of com- 
bustion is 60 per cent. 



250,000 (70 - 39) 260 X 24 
(70 + 15) 13,200 X 0.60 X 2000 



tons ' 



6 Which item may be determined more closely, the heating value of a fuel or 
the efficiency of its combustion? 

The^ heating values of oil, gas, and solid fuels are closely determinable, whereas the 
efficiency of burning depends on the particular equipment chosen and the skill used in 
handling it. 

7 In an office building, the thermostats are set to maintain 70 F from 7 a.m. 
to 5 p.m. and 50 F during the rest of the time. When the outside temperature 
is 30 F, how much saving might be expected because the temperatures are 
lowered? Under the above conditions the building becomes 50 F by 11 p.m. and 
warms up to 70 F by 8 a.m. 

A temperature of 70 F is maintained during 9 hours, and one of 50 F during 8 hours; the 
temperature would average about 60 F during the 7 hours required for cooling down and 
warming up. The average is 60.4 for the 24 hours. (The average temperature calcu- 
lated would have been 58.3 F, had the warming and cooling periods been neglected.) 



The saving is 1 X 100 = x 100 - 24 per cent. 

8 How does the heat capacity of a structure influence the saving made by 
carrying lower temperatures during the night? 

The heat storage capacity of the walls prevents rapid dropingof temperatures at night- 
time and delays the warming up process in the morning. In an extreme case, the building 
would not reach the lowered temperature by the time the higher temperature is called 
for in the morning. But under any conditions, the saving made by lowering the tem- 
perature can be correctly estimated by using the average temperature observed over the 
24-hour period as a factor, as in Question 7. 

9 What are some of the miscellaneous factors that may cause actual fuel 
consumption to vary from the theoretical fuel requirements as calculated by 
the use of heat losses, temperature difference, and fuel burning efficiency? 

The opening of windows; abnormally high or low inside temperatures; other sources of 
heat, such as machinery or lights; sun effect; high occupancy; and unusual winds. 

242 



Chapter 13 

HEATING BOILERS 

Cast-iron Boilers, Steel Boilers, Special Heating Boilers, 
Gas-Fired Boilers, Hot Water Supply Boilers, Furnace Design, 
Heating Surface, Testing and Rating Codes, Output Effic- 
iency, Selection of Boilers, Connections and Fittings, Erection, 
Operation and Maintenance, Boiler Insulation 

STEAM and hot water boilers for low pressure heating work are built in 
a wide variety of types, many of which are illustrated in the Catalog 
Data Section, and are classified as (1) cast-iron sectional, (2) steel fire 
tube, (3) steel water tube, and (4) special. 

CAST-IRON BOILERS 

Cast-iron boilers may be of round pattern with circular grate and hori- 
zontal pancake sections joined by push nipples and tie rods, or of rec- 
tangular pattern with vertical sections. The latter type may be either of 
outside header construction where each section is independent of the other 
and the water and steam connections are made externally through these 
headers, or assembled with push nipples and tie rods, in which case the 
water and steam connections are internal. 

Cast-iron boilers usually are shipped knocked down to facilitate hand- 
ling at the place of installation where assembly is made. One of the chief 
advantages of cast-iron boilers is that the separate sections can be taken 
into or out of basements and other places more or less inaccessible after 
the building is constructed. This feature is of importance in making 
repairs to or replacing a damaged or worn-out boiler and should be given 
consideration in the original selection. Sufficient space should be pro- 
vided in the boiler room for assembling the boiler and for disassembling it 
conveniently if repairs are needed. With the outside header type of boiler 
a damaged section in the middle of the boiler can be removed without 
disturbing the other sections so side clearance should be provided. 

Capacities of cast-iron boilers range from that required for small 
residences up to about 18,000 sq ft of steam radiation. For larger loads, 
cast-iron boilers must be installed in multiple, or a steel boiler must be 
used. In most cases cast-iron boilers are limited to working pressures of 
15 Ib for steam and 30 Ib for water. Special types are built for hot water 
supply which will withstand higher local water pressures. 

STEEL BOILERS 

Two general classifications may be applied to steel boilers: first, with 
regard to the relative position of water and hot gases, distinguished as fire 
tube or water tube; second, with regard to arrangement of furnace and 

243 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



flues, as (1) horizontal return tubular (HRT) boilers, (2) portable (self- 
contained) firebox boilers with either water or fire tubes, and (3) water 
tube boilers of the power type. 

Fire tube boilers are constructed so that the water available to produce 
steam is contained in comparatively large bodies distributed outside of the 
boiler tubes, the hot gases passing within the tubes. In water tube boilers, 
the water is circulated within the boiler tubes, heat being applied ex- 
ternally to them. 

The HRT boiler is the oldest type and consists of a horizontal cylin- 
drical shell with fire tubes, enclosed in brickwork to form the furnace and 

TABLE 1. PRACTICAL COMBUSTION RATES FOR SMALL COAL-FIRED HEATING BOILERS 
OPERATING ON NATURAL DRAFT OF FROM y% IN. TO y% IN. WATER* 



KIND OP COAL 


SQ FT GRATE 


LB or COAL PER SQ FT 
GRATE PER HOUR 


No. 1 Buckwheat Anthracite 


Up to 4 
5 to 9 
10 to 14 
15 to 19 
20 to 25 


3 

3H 
4 
&A 
5 


Anthracite Pea 


Up to 9 
10 to 19 
20 to 25 


5 
5Ji 
6 


Anthracite Nut and Larger 


Up to 4 
5 to 9 
10 to 14 
15 to 19 
20 to 25 


8 
9 
10 
11 
13 


Bituminous 


Up to 4 
5 to 14 
15 and above 


9.5 
12 
15.5 



aSteel boilers usually have higher combustion rates for grate areas exceeding 15 sq ft than those indicated 
in this table. 

combustion chamber. All heating surfaces and the interior of the boiler 
are accessible for both cleaning and inspection. Horizontal return tubular 
boilers, especially the larger sizes, should be suspended from structural 
columns and beams independent of the brick setting. Small HRT boilers 
sometimes are supported by brackets resting on the brick setting. 

Portable firebox boilers are the more generally used type of steel heating 
boilers, their outstanding characteristic being the water- jacketed firebox 
which eliminates virtually all brickwork. They are shipped in one piece 
from the factory and come to the job ready for immediate hook-up to 
piping. They may be of welded or riveted construction and have either 
water or fire tubes. Manufacturers' catalogs usually list heating surface 
as well as grate area. The elimination of brickwork also makes this type 
the most compact of steel boilers as well as the lowest in first cost. 

Water tube boilers. For large heating loads water tube boilers are quite 
frequently used. They usually require more head room than other types 
of boilers but require considerably less floor space and make possible a 

244 



CHAPTER 13. HEATING BOILERS 



much higher rate of evaporation per square foot of heating surface, with 
proper setting, baffling and draft. Water tube boilers used for heating 
purposes are either completely supported, insulated and encased in steel, 
or else brick set, supported on structural steel columns and have the brick 
setting encased in an insulated steel housing to prevent air infiltration and 
to minimize heat losses. For large heating loads at a high rate of evapora- 
tion, such boilers should be operated at pressures above 15 Ib per square 
inch with a pressure-reducing valve on the connection to the heating main. 

SPECIAL HEATING BOILERS 

A special type of boiler, known as the magazine feed boiler, has been 
developed for the burning of small sizes of anthracite and coke. These 
are built of both cast-iron and steel, and have a large fuel carrying 
capacity which results in longer firing periods than would be the case with 
the standard types using buckwheat sizes of coal. Special attention must be 
given to insure adequate draft and proper chimney sizes and connections. 

Oil-burner boiler units, in which a special boiler has been designed with 
a furnace shaped to meet the general requirements of oil burners or are 
specially adapted to one particular burner have been developed by a 
number of manufacturers. These usually are compact units with the 
burner and all controls enclosed within an insulated steel jacket. Ample 
furnace volume is provided for efficient combustion, and the heating 
surfaces are proportioned for effective heat transfer. Consequently, 
higher efficiencies are obtainable than with the ordinary coal fired boiler 
converted to oil firing. 

GAS-FIRED BOILERS 

Gas boilers have assumed a well-defined individuality. The usual boiler 
is sectional in construction with a number of independent burners placed 
beneath the sections. In most boilers each section has its own burner. In 
all cases the sections are placed quite closely together, much closer than 
would be possible when burning a soot-forming fuel. The effort of the 
designer is always to break the hot gas up into thin streams, so that all 
particles of the heat-carrying gases can come as close as possible to the 
heat-absorbing surfaces. Because there is no fuel bed resistance and because 
the gas company supplies the motive power to draw in the air necessary 
for combustion (in the form of the initial gas pressure) , draft losses through 
gas boilers are low. See Chapter 11. 

HOT WATER SUPPLY BOILERS 

Boilers for hot water supply are classified as direct, if the water heated 
passes through the boiler, and as indirect, if the water heated does not 
come in contact with the water or steam in the boiler. 

Direct heaters are built to operate at the pressures found in city supply 
mains and are tested at pressures from 200 to 300 Ib per square inch. 
The life of direct heaters depends almost entirely on the scale-making 
properties of the water supplied. If water temperatures are maintained 
below 140 F the life of the heater will be much longer than if higher 
temperatures are used, owing to decreased scale formation and minimized 
corrosion below 140 F. Direct water heaters in some cases are designed 
to burn refuse and garbage. 

245 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

Indirect heaters generally consist of steam boilers in connection with 
heat exchangers of the coil or tube types which transmit the heat from the 
steam to the water. This type of installation has the following advantages : 

1. The boiler operates at low pressure. 

2. The boiler is protected from scale and corrosion. 

3. The scale is formed in the heat exchanger in which the parts to which the scale 
is attached can be cleaned or replaced. The accumulation of scale does not affect 
efficiency although it will affect the capacity of the heat exchanger. 

4. Discoloration of water may be prevented if the water supply comes in contact 
with only non-ferrous metal. 

Where a steam heating system is installed, the domestic hot water 
usually is obtained from an indirect heater placed below the water line of 
the boiler. 

FURNACE DESIGN 

Good efficiency and proper boiler performance are dependent on cor- 
rect furnace design embodying sufficient volume for burning the par- 
ticular fuel at hand, which requires thorough mixing of air and gases at 
a high temperature with a velocity low enough to permit complete com- 
bustion of all the volatiles. On account of the small ampunt of volatiles 
contained in coke, anthracite, and semi-bituminous coal, these fuels can 
be burned efficiently with less furnace volume than is required for bi- 
tuminous coal, the combustion space being proportioned according to the 
amount of volatiles present. 

Combustion should take place before the gases are cooled by the boiler 
heating surface, and the volume of the furnace must be sufficient for this 
purpose. The furnace temperature must be maintained sufficiently high 
to produce complete combustion, thus resulting in a higher CO* content 
and the absence of CO. Hydrocarbon gases ignite at temperatures 
varying from 1000 to 1500 F. 

The question of furnace proportions, particularly in regard to mechani- 
cal stoker installations, has been given some consideration by various 
manufacturers' associations. 'Arbitrary values have been recommended 
for minimum dimensions. A customary rule-of -thumb method of figuring 
furnace volumes is to allow 1 cu ft of space for a maximum heat release 
of 50,000 Btu per hour. This value is equivalent to allowing approxi- 
mately 1 cu ft for each developed horsepower, and it is approved by 
most smoke prevention organizations. 

The setting height will vary with the type of stoker. In an overfeed 
stoker, for instance, all the volatiles must be burned in the combustion 
chamber and, therefore, a greater distance should be allowed than for an 
underfeed stoker where a considerable portion of the gas is burned while 
passing through the incandescent fuel bed. The design of the boiler also 
may affect the setting height, since in certain types the gas enters the 
tubes immediately after leaving the combustion chamber, while in others 
it passes ^over a bridge wall and toward the rear, thus giving a better 
opportunity for combustion by obtaining a longer travel before entering 
the tubes. 

_ To secure ^suitable furnace volume, especially for mechanical stokers or 
oil burners, it often is necessary either to pit the stoker or oil burner, or 

246 



CHAPTER 13. HEATING BOILERS 



where water line conditions and headroom permit, to raise the boiler on a 
brick foundation setting. 

Smokeless combustion of the more volatile bituminous coals is furthered 
by the use of mechanical stokers. (See Chapter 11.) Smokeless com- 
bustion in hand-fired boilers burning high volatile solid fuel is aided (1) 
by the use of double grates with down-draft through the upper grate, (2) 
by the use of a curtain section through which preheated auxiliary air is 
introduced over the fire toward the rear of the boiler, and (3) by the intro- 
duction of preheated air through passages at the front of the boiler. All 
three methods depend largely on mixing secondary air with the partially 
burned volatiles and causing this mixture to pass over an incandescent 
fuel bed, thus tending to secure more complete combustion than is pos- 
sible in boilers without such provision. 

HEATING SURFACE 

Boiler heating surface is that portion of the surface of the heat transfer 
apparatus in contact with the fluid being heated on one side and the gas or 
refractory being cooled on the other side. Heating surface on which the 
fire shines is known as direct or radiant surface and that in contact with 
hot gases only, as indirect or convection surface. The amount of heating 
surface, its distribution and the temperatures on either side thereof 
influence the capacity of any boiler. 

Direct heating surface is more valuable than indirect per square foot 
because it is subjected to a higher temperature and also, in the case of 
solid fuel, because it is in position to receive the full radiant energy of the 
fuel bed. The heat transfer capacity of a radiant heating surface may be 
as high as 6 to 8 times that of an indirect surface. This is one of the 
reasons why the water legs of some boilers have been extended, especially 
in the case of stoker firing where the extra amount of combustion chamber 
secured by an extension of the water legs is important. For the same 
reason, care should be exercised in building a refractory combustion 
chamber in an oil-burning boiler so as not to screen any more of this 
valuable surface with refractories than is necessary for good combustion. 

The effectiveness of the heating surface depends on its cleanliness, its 
location in the boiler, and the shape of the gas passages. Investigations 1 
by the U. S. Bureau of Mines show that: 

1. A boiler in which the heating surface is arranged to give long gas passages of small 
cross-section will be more efficient than a boiler in which the gas passages are short and of 
larger cross-section. 

2. The efficiency of a water tube boiler increases as the free area between individual 
tubes decreases and as the length of the gas pass increases. 

3. By inserting baffles so that the heating surface is arranged in series with respect to 
the gas flow, the boiler efficiency will be increased. 

The area of the gas passages must not be so small as to cause excessive 
resistance to the flow of gases where natural draft is employed. 

Heat Transfer Rates 

Practical rates of heat transfer in heating boilers will average about 
3300 Btu per sq ft per hour for hand-fired boilers and 4000 Btu per sq ft 



"See U. 5. Bureau of Mines Bulletin No. 18, The Transmission of Heat into Steam Boilers. 

247 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

per hour for mechanically fired boilers when operating at design load. 
When operating at maximum load 2 these values will run between 5000 and 
6000 Btu per sq ft per hour. Boilers operating under favorable conditions 
at the above heat transfer rates will give exit gas temperatures that are 
considered consistent with good practice. 

TESTING AND RATING CODES 

The Society has adopted three solid fuel testing codes, a solid fuel 
rating code and an oil fuel testing code. A.S.H.V.E. Standard and Short 
Form Heat Balance Codes for Testing Low-Pressure Steam Heating 
Solid Fuel Boilers Codes 1 and 2 (Revision of June 1929) 8 , are intended 
to provide a method for conducting and reporting tests to determine heat 
efficiency and performance characteristics. A.S.H.V.E. Performance 
Test Code for Steam Heating Solid Fuel Boilers Code No. 3 (Edition of 
1929) 8 is intended for use with A.S.H.V.E. Code for Rating Steam Heating 
Solid Fuel Hand-Fired Boilers 4 . The object of this test code is to specify 
the tests to be conducted and to provide a method for conducting and 
reporting tests to determine the efficiencies and performance of the boiler. 
The A.S.H.V.E. Standard Code for Testing Steam Heating Boilers 
Burning Oil Fuel 5 is intended to provide a standard method for con- 
ducting and reporting tests to determine the heating efficiency and per- 
formance characteristics when oil fuel is used with steam heating boilers. 

Steel Heating Boilers Ratings 

The Steel Heating Boiler Institute has adopted a method for the rating of 
low pressure boilers based on their physical characteristics and expressed 
in square feet of steam or water radiation or in Btu per hour as given in 
Table 2. The following requirements are included in this Code: 

1. One square foot of steam radiation is to be considered equal to the emission of 
240 Btu per hour and one square foot of water radiation is to be considered equal to 
emission of 150 Btu per hour. 

2. The rating of a boiler expressed in square feet of steam radiation in which solid fuel 
hand fired is used is based on the amount equal to 14 times the heating surface of the 
boiler in square feet. 

3. The rating of a boiler expressed in square feet of steam radiation in which solid fuel 
mechanically fired, or in which oil or gas is burned, is based on the amount equal to 
17 times the heating surface of the boiler in square feet. 

4. Heating surface is to be expressed in square feet and include those surfaces in the 
boiler which are exposed to the products of combustion on one side and water on the 
other. In measuring surfaces, the outer tube areas are to be considered. When a 
boiler has the water leg height increased the heating surface noted in the published 
ratings are not to be increased. 

5. A grate area is to be considered as an area of the grate surface expressed in square 
feet and measured in the plane of the top surface of the grate. For double grate boilers 
the grate surface is to be considered as the area of the upper grate plus one-quarter of the 
area of the lower grate. 

6. The grate area of a boiler for rating as determined in No. 2 is to be not less than 
that determined by the following formulae: 

For boilers with ratings 1800 sq ft to 4000 sq ft of steam radiation: 

Grate Area = ^/Catalogue Rating (in square feet steam radiation) 200 Q\ 



^/ 
M 



a For definitions of design load and maximum load see pages 251 and 252. 
'See A.S.H.V.E. TRANSACTIONS, Vol. 35, 1929, p. 12. Also Chapter 45. 
4 See A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 35. Also Chapter 45. 
*See A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 23* Also Chapter 45. 

24S 



CHAPTER 13. HEATING BOILERS 



TABLE 2. STANDARD STEEL HEATING BOILER RATINGS'* 



HAND FIRED CAPACITY RATING 



MECHANICALLY FIRED CAPACITY RATING 



Steam 
Radiation 
SqFt 


Water 
Radiation 
SqFt 


Btu per Hr 


Heating 
Surface 
SqFt 


Grate 
Area 
SqFt 


Steam 
Radiation 
SqFt 


w . : Furnace Volume 
Rg&j Btu^rHr *-&* 
^ Ft : CuFt 


1,800 


2,880 


432,000 


129 


7.9 ' 2,190 ! 3,500 , 525,600 , 15.7 


2,200 


3,520 


528,000 


158 


8.9 2,680 


4,280 j 643,200 19.2 


2,600 


4,160 


624,000 


186 


9.7 


3,160 5,050 ! 75S,400 , 22.6 


3,000 


4,800 


720,000 


215 


10.5 3,650 5,840 876.000 26.1 


3,500 


5,600 


840,000 


250 


11.4 , 4,250 6,800 1,020,000 30.4 


4,000 


6,400 


960,000 


286 


12.2 j 4,860 7,770 ; 1,166,400 34.8 


4,500 


7,200 


1,080,000 


322 


13.4 


5,470 ! 8,750 1,312,800 39.1 


5,000 


8,000 


1,200,000 


358 


14.5 


6,080 : 9,720 i 1,459,200 43.5 


6,000 


9,600 


1,440,000 


429 


16.4 


7,290 


11,660 1,749,600 


52.1 


7,000 


11,200 


1,680,000 


500 


18.1 


8,500 13,600 i 2,040,000 60.8 


8,500 


13,600 


2,OW,000 


608 


20.5 


10,330 


16,520 2,479,200 


73.8 


10,000 


16,000 


2,400,000 


715 


22.5 


12,150 19,440 


2,916.000 


86.8 


12,500 


20,000 


3,000,000 


893 


25.6 


15,180 24,280 


3,643,200 


108.5 


15,000 


24,000 


3,600,000 


1,072 


28.4 


18,220 


29,150 i 4,372,800 


130.2 


17,500 


28,000 


4,200,000 


1,250 


30.9 


21,250 


34,000 


5 T 100,000 


151.8 


20,000 


32,000 


4,800,000 


1,429 


33.2 


24,290 


38,860 


5,829,600 


173.5 


25,000 


40,000 


6,000,000 


1,786 


37.4 


30,360 


48,570 


7,286,400 


216.9 


30,000 


48,000 


7,200,000 


2,143 


41.2 


36,430 


58,280 


8,743,200 


260.3 


35,000 


56,000 


8,400,000 


2,500 


44.7 


42,500 


68,000 


10,200,000 


303.6 



aAdopted by the Steel Heating Boiler Institute in cooperation with the Bureau of Standards, United States 
Department of Commerce Simplified Practice Recommendation R 157-S5. 

For boilers with ratings 4000 sq ft of steam radiation and larger: 



Grate Area 



V Catalogue Rating (in square feet steam radiation) 1500 
16.8 



7. The volume for furnaces in which solid fuel is burned is to be considered as the 
cubical content of the space between the bottom of the fuel bed and the first plane of 
entry into or between the tubes. Volume of furnaces in which pulverized liquid fuel or 
gaseous fuel is burned are to be considered as the cubical content of the space between 
the hearth and the first plane of entry into or between the tubes. No minimum furnace 
volume is to be specified for mechanical fired boilers burning anthracite. 

8. The furnace volume for a boiler, with a rating as determined in No. 3 in^which oil, 
gas or bituminous coal stoker fired is burned is not to be less than one cubic foot for 
every 140 sq ft of steam rating. 

9. The average height of furnace for the rating determined in No. 3 in which bitu- 
minous coal, stoker fired is burned is not to be less than that determined graphically in 
Fig. 1 or mathematically by the following formula: 



(3) 



where 

H average furnace height, inches as determined by the following formula; 

12F 12F 



H 



WL 



R = stoker fired boiler rating, square foot steam radiation. 

A = plan area of firebox, square feet measured at the bottom of the fuel bed. 

F = furnace volume, cubic feet. 

249 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



W = average width of furnace, measured at the bottom of the fuel bed, feet. 
L length of furnace, feet. If the furnace is longer than the fuel bed or contains a 
bridge wall, the total length of the furnace may be used except that this length 
is not to exceed 2 J W. 

BOILER OUTPUT 

Boiler output as defined in A.S.H.V.E. Performance Test Code for 
Steam Heating Solid Fuel Boilers (Code No. 3) is the quantity of heat 
available at the boiler nozzle with the boiler normally insulated. It 
should be based on actual tests conducted in accordance with this code. 
This output is usually stated in Btu and in square feet of equivalent heat- 
ing surface (radiation). According to the A.S.H.V.E. Standard Code for 




PLAN AREA OF FURNACE, SQUARE FEET 



FIG. 1. FURNACE HEIGHTS FOR STOKER FIRED BOILERS AND BITUMINOUS COAL 
RATED IN SQUARE FEET STEAM RADIATION 



Rating Steam Heating, Solid Fuel, Hand-Fired Boilers, the performance 
data should be given in tabular or curve form on the following items for at 
least five outputs ranging from maximum down to 35 per cent of maxi- 
mum: (1) fuel available, (2) combustion rate, (3) efficiency, (4) draft 
tension, (5) flue gas temperature. The only definite restriction placed on 
setting the maximum output is that priming shall not exceed 2 per cent. 
These curves provide complete data regarding the performance of the 
boiler under test conditions. Certain other pertinent information, such as 
grate area, heating surface and chimney dimensions is desirable also in 
forming an opinion of how the boiler will perform in actual service. 

The output of large heating boilers is frequently stated in terms of 
boiler horsepower instead of in Btu per hour or square feet of equivalent 
radiation. 

250 



CHAPTER 13. HEATING BOILERS 



Boiler Horsepower : The evaporation of 34.5 Ib of water per hour 
from and at 212 F which is equivalent to a heat output of 970.2 X 34.5 = 
33,471.9 Btu per hour. 

Equivalent Evaporation : The amount of water a boiler would 
evaporate, in pounds per hour, if it received feed water at 212 F and 
vaporized it at this same temperature and at atmospheric pressure. 

It is usually considered that 10 sq ft of boiler heating surface will pro- 
duce a rated boiler horsepower. A rated boiler horsepower in turn 
can carry a design load of from 100 to 140 sq ft of equivalent radiation. 
It is apparent, therefore, that 1 sq ft of boiler heating surface can carry a 
design load of from 10 to 14 sq ft of equivalent radiation, or somewhat 
more if the boiler is forced above rating. The application of these values 
is discussed under the heading Selection of Boilers. 

BOILER EFFICIENCY 

The term efficiency as used for guarantees of boiler performance is 
usually construed as follows: 

1. Solid Fuels. The efficiency of the boiler alone is the ratio of the heat absorbed by 
the water and steam in the boiler per pound of combustible burned on the grate to the 
calorific value of 1 Ib of combustible as fired. The combined, efficiency of boiler, furnace 
and grate is the ratio of the heat absorbed by the water and steam in the boiler per pound 
of fuel as fired to the calorific value of 1 Ib of fuel as fired. 

2. Liquid Fuels. The combined efficiency of boiler, furnace and burner is the ratio of 
the heat absorbed by the water and steam in the boiler per pound of fuel to the calorific 
value of 1 Ib of fuel. 

Solid fuel boilers usually show an efficiency of 50 to 75 per cent when 
operated under favorable conditions at their rated capacities. Infor- 
mation on the combined efficiencies of boiler, furnace and burner has 
resulted from research conducted at Yale University in cooperation with 
the A.S.H.V.E, Research Laboratory and the American Oil Burner 
Association*. 

SELECTION OF BOILERS 

Estimated Design Load : The load, stated in Btu per hour or equiva- 
lent direct radiation, as estimated by the purchaser for the conditions of 
inside and outside temperature for which the amount of installed radiation 
was determined is the sum of the heat emission of the radiation to be 
actually installed plus the allowance for the heat loss of the connecting 
piping plus the heat requirement for any apparatus requiring heat con- 
nected with the system (A.S.H.V.E. Standard Code for Rating Steam 
Heating Solid Fuel Hand-Fired Boilers Edition of April, 1932). 

The estimated design load is the sum of the following three items 7 : 

1. The estimated heat emission in Btu per hour of the connected radiation (direct, 
indirect or central fan) to be installed. 

2. The estimated maximum heat in Btu per hour required to supply water heaters 
or other apparatus to be connected to the boiler. 



6 Study of the Characteristics of Oil Burners and Heating Boilers, by L. E. Seeley and E. J. Tavanlar 
(A.S.H.V.E. TRANSACTIONS, Vol. 37, 1931, p. 517), A Study of Intermittent Operation of Oil Burners, by L. 
E. Seeley and J. H. Powers (A.S.H.V.E. TRANSACTIONS, Vol. 38, 1932, p. 317). 

7 A.S.H.V.E. Code of Minimum Requirements for the Heating and Ventilation of Buildings (Edition 
of 1929). 

251 



HEATING VENTILATING Am CONDITIONING GUIDE 1938 

3. The estimated heat emission in Btu per hour of the piping connecting the radiation 
and other apparatus to the boiler. 

Estimated Maximum Load : Construed to mean the load stated in 
Btu per hour or the equivalent direct radiation that has been estimated by 
the purchaser to be the greatest or maximum load that the boiler will be 
called upon to carry. (A.S.H.V.E. Standard Code for Rating Steam 
Heating Solid Fuel Hand-Fired Boilers Edition of April, 1932.) 

The estimated maximum load is given by 8 : 

4. The estimated increase in the normal load in Btu per hour due to starting up cold 
radiation. This percentage of increase is to be based on the sum of Items 1, 2 and 3 
and the heating-up factors given in Table 3. 

TABLE 3. WARMING-UP ALLOWANCES FOR Low PRESSURE STEAM AND 
HOT WATER HEATING BoiLERsai b i c 



DESIGN LOAD (REPRESENTING STJMMA/TION OF ITEMS 1, 2, AND 3,d 


PESCENTAOE CAPACITY TO ADD 
FOR WABMINO UP 


Btu per Hour 


Equivalent Square Feet of Radiation* 


Up to 100,000 
100,000 to 200,000 
200,000 to 600,000 
600,000 to 1,200,000 
1,200,000 to 1,800,000 
Above 1,800,000 


Up to 420 
420 to 840 
840 to 2500 
2500 to 5000 
5000 to 7500 
Above 7500 


65 
60 
55 
50 
45 . 
40 



aThis table is taken from the A.S.H.V.E. Code of Minimum Requirements for the Heating and Venti- 
lation of Buildings, except that the second column has been added for convenience in interpreting the design 
load in terms of equivalent square feet of radiation. 

bSee also Time Analysis in Starting Heating Apparatus, by Ralph C. Taggert (A.S.H.V.E. TRANSAC- 
TIONS, Vol. 19, 1913, p. 292); Report of A.S.H.V.E. Continuing Committee on Codes for Testing and Rating 
Steam Heating Solid Fuel Boilers (A.S.H.V.E. TRANSACTIONS, Vol. 36, 1930, p. 35) ; Selecting the Right 
Size Heating Boiler, by Sabin Crocker (Heating, Piping and Air Conditioning, March, 1932). 

cThis table refers to hand-fired, solid fuel boilers. A factor of 20 per cent over design load is adequate 
when automatically-fired fuels are used (see Fig. 3). 

d240 Btu per square foot. 

Other things to be considered are: 

5. Efficiency with hard or soft coal, gas, or oil firing, as the case may be. 

6. Grate area with hand-fired coal, or fuel burning rate with stokers, oil, or gas. 

7. Combustion space in the furnace. 

8. Type of heat liberation, whether continuous or intermittent, or a combination of 
both. 

9. Miscellaneous items consisting of draft available, character of attendance, pos- 
sibility of future extension, possibility of breakdown and headroom in the boiler room. 

Radiation Load 

The connected radiation (Item 1) is determined by calculating the^heat 
losses in accordance with data given in Chapters 5, 6 and 7, and dividing 
by 240 to change to square feet of equivalent radiation as explained in 
Chapter 14. For hot water, the emission commonly used is 150 Btu per 
square foot, but the actual emission depends on the temperature of the 
medium in the heating units and of the surrounding air. (See Chapter 14.) 

Although it is customary to use the actual connected load in equivalent 
square feet of radiation for selecting the size of boiler, this connected load 
usually represents a reserve in heating capacity to provide for infiltration 
in the various spaces of the building to be heated, which reserve, however, 

8 Loc. Cit. Note 7. 

252 



CHAPTER 13. HEATING BOILERS 



is not in use at all places at the same time, or in any one place at all times. 
For a further discussion of this subject see Chapter 6. 

Hot Water Supply Load 

When the hot water supply (Item 2) is heated by the building heating 
boiler, this load must be taken into consideration in sizing the boiler. The 




0.6 60 



^0.3 5 |5|4.5 

OK < |j 

So-2 ^40 * 105 a 

LI i.it 



1000 



3OOO 



OUTPUT. SQ. FT, EQUIVALENT STEAM RADIATION (240 BTU PER 3Q. FT.) 

BOILER DATA- CRATE AREA.SQ.FT. 16-0 FUEL-BITUMINOUS 3/4- LUMP 

HEATING SURFACE.SQ FT. 254 ANALYSIS- VOLATILE MATTER 34.687. 

WEIGHT, LB. 0160 FIXED CARBON 35-44 

FUEL CAPACITY. LB. 63. ASH 9.97 

FUEL AVAIL ABLE, LB. 414. SULPHUR 2.6 

. io 



FIG 2 TYPICAL PERFORMANCE CURVES FOR A 36-iN. CAST-IRON SECTIONAL STEAM 

HEATING BOILER, BASED ON THE A.S.H.V.E. CODE FOR RATING STEAM 

HEATING SOLID FUEL HAND-FIRED BOILERS 

allowance to be made will depend on the amount of water heated and its 
temperature rise. A good approximation is to add 4 sq ft of equivalent 
radiation for each gallon of water heated per hour through a temperature 
range of 100 F. For more specific information, see Chapter 43. 

Piping Tax (Item 3) 

It is common practice to add a flat percentage allowance to the 
equivalent connected radiation to provide for the heat loss from bare and 
covered pipe in the supply and return lines. The use of a flat allowance of 
25 per cent for steam systems and 35 per cent for hot water systems is 
preferable to ignoring entirely the load due to heat loss from the supply 

253 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

and return lines, but better practice, especially when there is much bare 
pipe, is to compute the emission from both bare and covered pipe surface 
in accordance with data in Chapter 39. A chart is shown in Fig. 3 indicat- 
ing percentage allowances for piping and warming-up which are applic- 
able to automatically-fired heating plants using steam radiation. With 
direct radiation served by bare supply and return piping the percentages 
may be higher than those stated, while in the case of unit heaters where 
the output is concentrated in a few locations/ the piping tax may be 
10 per cent or less. 




10 12 14 

NET LOAD, STEAM RADIATION, THOUSAND SQ FT 



18 



FIG. 3. PERCENTAGE ALLOWANCE FOR PIPING AND WARMING-UP 



Warming-Up Allowance 

The warming-up allowance represents the load due to heating the boiler 
and contents to operating temperature and heating up cold radiation and 
piping. (See Item 4.) The factors to be used for determining the 
allowance to be made should be selected from Table 3 and should be 
applied to the estimated design load as determined by Items 1, 2 and 3. 
While in every case the estimated maximum load will exceed the design 
load if adequate heating response is to be achieved, there is however, no 
object in over-estimating the allowances, as the only effect would be to 
reduce the time of warming-up by a few minutes. Otherwise, it might 
result in firing the boiler unduly and increasing the cost of operation. 

Performance Curves for Boiler Selection 

In the selection of a boiler to meet the estimated load, the A.S.H.V.E. 



Standard Code for Rating Steam Heating Solid Fuel Hand-Fired Boilers 
recommends the use of performance curves based on actual tests con- 
ducted in accordance with the A.S.H.V.E. Performance Test Code for 
Steam Heating Solid Fuel Boilers (Code No. 3), similar to the typical 
curves shown in Fig. 2. It should be understood that performance data 
apply to test conditions and that a reasonable allowance should be made 
for decreased output resulting from soot deposit, poor fuel or inefficient 
attention. 

254 



CHAPTER 13. HEATING BOILERS 



Selection Based on Heating Surface and Grate Area 

Where performance curves are not available, a good general rule for 
conventionally-designed boilers is to provide 1 sq ft of boiler heating 
surface for each 14 sq ft of equivalent radiation (240 Btu per square foot) 
represented by the design load consisting of connected radiation, piping 
tax and domestic water heating load. As stated in the section on Boiler 
Output, this is equivalent to allowing 10 sq ft of boiler heating surface per 
boiler horsepower. In this case it is assumed that the maximum load 
including the warming-up allowance will be provided for by operating the 
boiler in excess of the design load, that is, in excess of the 100 per cent 
rating on a boiler-horsepower basis. 

Due to the wide variation encountered in manufacturers' ratings for 
boilers of approximately the same capacity, it is advisable to check the 
grate area required for heating boilers burning solid fuel by means of the 
following formula: 

TT 

G = CXFXE (4) 

where 

G = grate area, square feet. 

H = required total heat output of the boiler, Btu per hour (see Selection of Boilers, 

p. 251). 
C combustion rate in pounds of dry coal per square foot of grate area per hour, 

depending on the kind of fuel and size of boiler as given in Table 1. 
F calorific value of fuel, Btu per pound. 
E = efficiency of boiler, usually taken as 0.60. 

Example 1. Determine the grate area for a required heat output of the boiler of 
500,000 Btu per hour, a combustion rate of 6 Ib per hour, a calorific value of 13,000 Btu 
per pound, and an efficiency of 60 per cent. 



The boiler selected should have a grate area not less than that deter- 
mined by Formula 4. With small boilers where it is desired to provide 
sufficient coal capacity for approximately an eight-hour firing period plus 
a 20 per cent reserve for igniting a new charge, more grate area may be 
required depending upon the depth of the fuel pot. 

Selection of Steel Heating Boilers 

Boiler ratings previously described under the Steel Heating Boiler 
Institute's Boiler Rating Code are intended to correspond with the esti- 
mated design load based on the sum of items 1, 2 and 3 outlined on pages 
252 and 253. Insulated residence type boilers for oil or gas may carry 
a net load expressed in square feet of steam radiation of not more than 
17 times the square feet of heating surface in the boiler, provided the 
boiler manufacturer guarantees the boiler to be capable of operating at a 
maximum output of not less than 150 per cent of net load rating with over- 
all efficiency of not less than 75 per cent with at least two different makes 
of each type of standard commercial burner recommended by the boiler 
manufacturer. If the heat loss from the piping system exceeds 20 per cent 
of the installed radiation, the excess is to be considered as a part of the net 
load. 

255 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



When the estimated heat emission of the piping (connecting radiation, 
and other apparatus to the boiler) is not known the net load to be con- 
sidered for the boiler may be determined from Table 4. 

Selection of Gas-Fired Boilers 

Gas-heating appliances should be selected in accordance with the 
percentage allowances given in Fig. 3. These factors are for thermo- 
statically-controlled systems; in case manual operation is desired, a 
warming-up allowance of 100 per cent is recommended by the A.G.A. 
A gas boiler selected by the use of the A.G.A. factors will be the minimum 

TABLE 4. BOILER RATINGS BASED ON NET LoAD a 



HAJTD FIRED RATINGS 


MECHANICALLY FIRED RATINGS 


Steam Radiation Sq Ft 


Net Loadb 
Steam Radiation Sq Ft 


Steam Radiation Sq Ft 


Net Loadb 
Steam Radiation Sq Ft 


1,800 


1,389 


2,190 


1,695 


2,200 


1,702 


2,680 


2,089 


2,600 


2,020 


3,160 


2,461 


3,000 


2,335 


3,650 


2,853 


3,500 


2,732 


4,250 


3,335 


4,000 


3,135 


4,860 


3,830 


4,500 


3,540' 


5,470 


4,330 


5,000 


3,945 


6,080 


4,834 


6,000 


4,770 


7,290 


5,850 


7,000 


5,608 


8,500 


6,885 


8,500 


6,885 


10,330 


8,490 


10,000 


8,197 


12,150 


10,125 


12,500 


10,417 


15,180 


12,650 


15,000 


12,500 


18,220 


15,183 


17,500 


14,584 


21,250 


17,708 


20,000 


16,667 


24,290 


20,242 


25,000 


20,834 


30,360 


25,300 


30,000 


25,000 


36,430 


30,359 


35,000 


29,167 


42,500 


35,417 



aAdopted by the Steel Heating Boiler Institute in cooperation with the Bureau of Standards , United States 
Department of Commerce Simplified Practice Recommendation R 157-35. 

bThe net load is made up by the sum of the estimated design load, items 1 and 2 (pages 252 and 253). All 
net loads are expressed in 70 F. For hand fired boiler ratings less than 1800 sq ft of steam or 2880 sq. ft of 
water and mechanically fired boiler ratings of 2190 sq ft of steam or 3500 sq ft of water, apply the factor 
1.3 to the net load to determine the boiler size. For water boilers use the equivalent net load for steam 
boilers of similar physical size. 

size boiler which can carry the load. From a fuel economy standpoint, it 
may be advisable to select a somewhat larger boiler and then throttle the 
gas and air adjustments as required. This will tend to give a low stack 
temperature with high efficiency and at the same time provide reserve 
capacity in case the load is under-estimated or more is added in the future. 

Conversions 

The conversion of a coal or oil boiler to gas burning is simpler than the 
reverse since little furnace volume need be provided for the proper com- 
bustion of gas. When a solid fuel boiler of 500 sq ft (or less) capacity is 
converted to gas burning, the necessary gas heat units should be approxi- 
mately double the connected load. The presumption for a conversion 
job is that the boiler is installed and probably will not be made larger; 

256 



CHAPTER 13. HEATING BOILERS 



therefore, it is a matter of setting a gas-burning rate to obtain best results 
with the available surface. Assuming a combustion efficiency of 75 per 
cent for a conversion installation the boiler output would be 2 X 0.75 
= 1.5 times the connected load, which allows 50 per cent for piping tax 
and pickup. In converting large boilers, the determination of the re- 
quired Btu input should not be done by an arbitrary figure or factor but 
should be based on a detailed consideration of the requirements and 
characteristics of the connected load. 

An efficient conversion installation depends upon the proper size of 
flue connection. Often the original smoke breeching between the boiler 
and chimney is too large for gas firing, and in this case, flue orifices can be 
used. They are discs provided with an opening of the size for the gas 
input used in this boiler. The size should be based on 1 sq in. of flue area 
for each 7500 hourly Btu input. 

If dampers are found in the breeching they should be locked in position 
so that they will not interfere with the normal operation of the gas burners 
at maximum flow. In the case of large boiler conversions, automatic 
damper regulators proportion the position of the flue dampers to the 
amount of gas flowing and may be substituted for existing dampers. 
Generally in residence conversions automatic dampers are not of the 
proportioning type but close the flue during the off periods of the gas 
burners. Automatic shutoff dampers should be located between the 
backdraft diverter and the chimney flue. Automatic dampers are usually 
designed to operate with electric contact mechanism, but frequently an 
arrangement is utilized which functions with mechanical fluid or gas 
pressure. 

Physical Limitations 

As it will usually be found that several boilers will meet the speci- 
fications, the final selection of the boiler may be influenced by other con- 
siderations, some of which are: 

1. Dimensions of boiler. 

2. Durability under service. 

3. Convenience in firing and cleaning. 

4. Adaptability to changes in fuel and kind of attention. 

5. Height of water line. 

In large installations, the use of several smaller boiler units instead of 
one larger one will obtain greater flexibility and economy by permitting 
the operation, at the best efficiency, of the required number of units 
according to the heat requirements. 

Space Limitations 

Boiler rooms should, if possible, be situated at a central point with 
respect to the building and should be designed for a maximum of natural 
light. The space in front of the boilers should be sufficient for firing, 
stoking, ash removal and cleaning or renewal of flues, and should be at 
least 3 ft greater than the length of the boiler firebox. 

A space of at least 3 ft should be allowed on at least one side of every 
boiler for convenience of erection and for accessibility to the various 

257 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

dampers, cleanouts and trimmings. The space at the rear of the boiler 
should be ample for the chimney connection and for cleanouts. With 
large boilers the rear clearance should be at least 3 ft in width. 

The boiler room height should be sufficient for the location of boiler 
accessories and for proper installation of piping. In general the ceiling 
height for small steam boilers should be at least 3 ft above the normal 
boiler water line. With vapor heating, especially, the height above the 
boiler water line is of vital importance. 

When steel boilers are used, space should be provided for the removal 
and replacement of tubes. 

CONNECTIONS AND FITTINGS 

The velocity of flow through the outlets of low pressure steam heating 
boilers should not exceed 15 to 25 fps if fluctuation of the water line and 
undue entrainment of moisture are to be avoided. Steam or water outlet 
connections preferably should be the full size of the manufacturers' 
tapping and should extend vertically to the maximum height available 
above the boiler. For gravity circulating steam heating systems, it is 
recommended that a Hartford Loop, described in Chapter 16, be utilized 
in making the return connection. 

Particular attention should be given to fitting connections to secure con- 
formity with the A.S.MJS. Boiler Construction Code for Low Pressure 
Heating Boilers. Attention is called in particular to pressure gage piping, 
water gage connections and safety valve capacity. 

Steam gages should be fitted with a water seal and a shut-off consisting 
of a cock with either a tee or lever handle which is parallel to the pipe 
when the cock is open. Steam gage connections should be of copper or 
brass when smaller than 1 in. I.P.S. 9 if the gage is more than 5 ft from the 
boiler connection, and also in any case where the connection is less than 
M in. I.P.S. 

Each steam or vapor boiler should have at least one water gage glass and 
two or more gage cocks located within the range of the visible length of the 
glass. The water gage fittings or gage cocks may be direct connected to 
the boiler, if so located by the manufacturer, or may be mounted on a 
separate water column. No connections, except. for combustion regu- 
lators, drains or steam gages, should be placed on the pipes connecting 
the water column and the boiler. If the water column or gage glass is con- 
nected to the boiler by pipe and fittings, a cross, tee or equivalent, in which 
a deanout plug or a drain valve and piping may be attached, should be 
placed in the water connection at every right-angle turn to facilitate 
cleaning. The water line in steam boilers should be carried at the level 
specified by the boiler manufacturer. 

Safety valves should be capable of discharging all the steam that can be 
generated by the boiler without allowing the pressure to rise more than 
5 Ib above the maximum allowable working pressure of the boiler. This 
should be borne in mind particularly in the case of boilers equipped with 
mechanical stokers or oil burners where the amount of grate area has 
little significance as to the steam generating capacity of the boiler. 



'A3.M.E. Code, Identification of Piping Systems. 

258 



CHAPTER 13. HEATING BOILERS 



Where a return header is used on a cast-iron sectional boiler to distribute 
the returns to both rear tappings, it is advisable to provide full size 
plugged tees instead of elbows where the branch connections enter the 
return tappings. This facilitates cleaning sludge from the bottom of the 
boiler sections through the large plugged openings. An equivalent clean- 
out plug should be provided in the case of a single return connection. 

Blow-off or drain connections should be made near the boiler and so 
arranged that the entire system may be drained of water by opening the 
drain cock. In the case of two or more boilers separate blow-off connec- 
tions must be provided for each boiler on the boiler side of the stop valve 
on the main return connection. 

Water service connections must be provided for both steam and water 
boilers, for refilling and for the addition of make-up water to boilers. This 
connection is usually of galvanized steel pipe, and is made to the return 
main near the boiler or boilers. 

For further data on pipe connections for steam and hot water heating 
systems, see Chapters 16 and 17 and thtA.S.M.E. Boiler Construction 
Code for Low Pressure Heating Boilers. 

Smoke Breeching and Chimney Connections. The breeching or smoke 
pipe from the boiler outlet to the chimney should be air- tight and as short 
and direct as possible, preference being given to long radius and 45-deg 
instead of 90-deg bends. The breeching entering a brick chimney should 
not project beyond the flue lining and where practicable it should be 
grouted from the inside of the chimney. A thimble or sleeve grout 
usually is provided where the breeching enters a brick chimney. 

Where a battery of boilers is connected into a breeching each boiler 
should be provided with a tight damper. The breeching for a battery 
of boilers should not be reduced in size as it goes to the more remote 
boilers. Good connections made to a good chimney will usually result in 
a rapid response by the boilers to demands for heat. 

ERECTION, OPERATION, AND MAINTENANCE 

The directions of the boiler manufacturer always should be read before 
the assembly or installation of any boiler is started, even though the 
contractor may be familiar with the boiler. All joints requiring boiler 
putty or cement which cannot be reached after assembly is complete 
must be finished as the assembly progresses. 

The following precautions should be taken in all installations to prevent 
damage to the boiler: 

1. There should be provided proper and convenient drainage connections for use if 
the boiler is not in operation during freezing weather. 

2. Strains on the boiler due to movement of piping during expansion should ^ be 
prevented by suitable anchoring of piping and by proper provision for pipe expansion 
and contraction. 

3. Direct impingement of too intense local heat upon any part of the boiler surface, 
as with oil burners, should be avoided by protecting the surface with firebrick or other 
refractory material. 

4. Condensation must flow back to the boiler as rapidly and uniformly as possible. 
Return connections should prevent the water from backing out of the boiler. 

5. Automatic boiler feeders and low water cut-off devices which shut off the source 

259 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

of heat if the water in the boiler falls below a safe level are recommended for boilers 
mechanically fired. 

Boiler Troubles 

A complaint regarding boiler operation generally will be found to be 
due to one of the following: 

1. The boiler fails to deliver enough heat. The cause of this condition may be: (a) poor 
draft; (&) poor fuel; (c) inferior attention or firing; (d) boiler too small; (e) improper 
piping; (f) improper arrangement of sections; (g) heating surfaces covered with soot; 
and (h) insufficient radiation installed. 

2. The water line is unsteady. The cause of this condition may be: (a) grease and dirt 
in boiler; (b) water column connected to a very active section and, therefore, not 
showing actual water level in boiler; and (d) boiler operating at excessive output. 

3. Water disappears from gage glass. This may be caused by: (a) priming due to 
grease and dirt in boiler; (b) too great pressure difference between supply and return 
piping preventing return of condensation; (c) valve closed in return line; (d) connection 
of bottom of water column into a very active section or thin waterway; and (e) improper 
connections between boilers in battery permitting boiler with excess pressure to push 
returning condensation into boiler with lower pressure. 

4. Water is carried over into steam main. This may be caused by: (a) grease and dirt 
in boiler; (b) insufficient steam dome or too small steam liberating area; (c) outlet con- 
nections of too small area; (d) excessive rate of output; and (e) water level carried 
higher than specified. 

5. Boiler is slow in response to operation of dampers. This may be due to: (a) poor 
draft resulting from air leaks into chimney or breeching; (b) inferior fuel; (c) inferior 
attention; (d) accumulation of clinker on grate; and (e) boiler too small for the load. 

6. Boiler requires^ too frequent cleaning of flues. This may be due to: (a) poor draft; 
(6) smoky combustion; (c) too low a rate of combustion; and (d) too much excess air 
in firebox causing chilling of gases. 

7. Boiler smokes through fire door. This may be due to: (a) defective draft in chimney 
or incorrect setting of dampers; (b) air leaks into boiler or breeching; (c) gas outlet from 
firebox plugged with fuel; (d) dirty or clogged flues; and (e) improper reduction in 
breeching size. 

Cleaning Steam Boilers 

All boilers are provided with flue clean-out openings through which the 
heating surface^ can be reached by means of brushes or scrapers. Flues 
of solid fuel boilers should be cleaned often to keep the surfaces free of 
soot or ash. Gas boiler flues and burners should be cleaned at least once 
a year. Oil burning boiler flues should be examined periodically to deter- 
mine when cleaning is necessary. 

The grease used to lubricate the cutting tools during erection of new 
piping systems serves as a carrier for sand and dirt, with the result that 
a scum of fine particles and grease accumulates on the surface of the 
water in all new boilers, while heavier particles may settle to the bottom 
of the boiler and form sludge. These impurities have a tendency to cause 
foaming, preventing the generation of steam and causing an unsteady 
water line. 

This unavoidable accumulation of oil and grease should be removed 
by blowing off the boiler as follows: If not already provided, install a 
surface blow connection of at least 1% in. nominal pipe size with outlet 
extended to within 18 in. of the floor or to sewer, inserting a valve in line 
close to boiler. Bring the water line to center of outlet, raise steam pres- 
sure and while fire is burning briskly open valve in blow-off line. When 

260 



CHAPTER 13. HEATING BOILERS 



pressure recedes close valve and repeat process adding water at intervals 
to maintain proper level. As a final operation bring the pressure in the 
boiler to about 10 Ib, close blow-off, draw the fire or stop burner, and open 
drain valve. After boiler has cooled partly, fill and flush out several times 
before filling it to proper water level for normal service. The use of soda, 
or any alkali, vinegar or any acid is not recommended for cleaning heating 
boilers because of the difficulty of complete removal and the possibility 
of subsequent injury, after the cleaning process has been completed. 

Insoluble compounds have been developed which are effective, but 
special instructions on the proper cleaning compound and directions for 
its use in a boiler, as given by the boiler manufacturer, should be carefully 
followed. 

It is common practice when starting new installations to discharge 
heating returns to the sewer during the first week of operation. This 
prevents the passage of grease, dirt or other foreign matter into the boiler 
and consequently may avoid the necessity of cleaning the boiler. During 
the time the returns are being passed to the sewer, the feed valve should 
be cracked sufficiently to maintain the proper water level in the boiler. 

Care of Idle Heating Boilers 

Heating boilers are often seriously damaged during summer months 
due chiefly to corrosion resulting from the combination of sulphur from 
the fuel with the moisture in the cellar air. At the end of the heating 
season the following precautions should be taken: 

1. All heating surfaces should be cleaned thoroughly of soot, ash and residue, and the 
heating surfaces of steel boilers should be given a coating of lubricating oil on the ore 
side. 

2. All machined surfaces should be coated with oil or grease. 

3. Connections to the chimney should be cleaned and in case of small boilers the pipe 
should be placed in a dry place after cleaning. 

4. If there is much moisture in the boiler room, it is desirable to drain the boiler to 
prevent atmospheric condensation on the heating surfaces of the boiler when they are 
below the dew-point temperature. Due to the hazard of some one inadvertently building 
a fire in a dry boiler, however, it is safer to keep the boiler filled with water. A hot water 
system usually is left filled to the expansion tank. 

5. The grates and ashpit should be cleaned. 

6. Clean and repack the gage glass if necessary. 

7. Remove any rust or other deposit from exposed surfaces by scraping with a wire 
brush or sandpaper. After boiler is thoroughly cleaned, apply a coat of preservative 
paint where required to external parts normally painted. 

8. Inspect all accessories of the boiler carefully to see that they are in good working 
order. In this connection, oil all door hinges, damper bearings and regulator parts. 

BOILER INSULATION 

Insulation for cast-iron boilers is of two general types: (1) plastic 
material or blocks wired on, cemented and covered with canvas or duck; 
and (2) blocks, sheets or plastic material covered with a metal jacket 
furnished by the boiler manufacturer. Self-contained steel firebox boilers 
usually are insulated with blocks, cement and canvas, or rock wool 
blankets; HRT boilers are brick set and do not require insulation beyond 
that provided in the setting. It is essential that the insulation on a boiler 

261 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

and adjacent piping be of non-combustible material as even slow-burning 
insulation constitutes a dangerous fire hazard in case of low water in 
the boiler. 

PROBLEMS IN PRACTICE 

1 What basic requirements of boiler design are to be accomplished with a 
combination, boiler and oil burner unit? 

Combination units vary widely but in general, the basic requirements of design depends 
upon a combustion chamber of proper design and arranged for the flame shape with 
adequate heating surface for the complete combustion of the fuel. 

2 What is the normal rating range of each type of boiler? 

a. Cast-iron boilers are rated at from 200 to 18,000 sq ft EDR. 

b. Steel boilers are rated at from 300 to 50,000 sq ft EDR. 

3 What factors contribute to economical fuel operation in low pressure 
boilers burning coal or oil? 

a. Proper furnace volume for complete combustion. 

b. Arrangement of heating surfaces in series to create a turbulent and scrubbing contact 
of gases against the convective surfaces. 

c. Rapid internal water circulation which will remove steam bubbles from the water 
side of heating surfaces and allow other steam bubbles to be formed. Rapid disen- 
gagement of steam bubbles increases the steam generating efficiency of each unit 
area of heating surface, and thereby lowers flue gas temperatures. 

4 What ecpiipment is usually directly attached to a low pressure heating 
boiler? 

For coal burning steam boilers: water column, water gage, tri-cocks, steam gage, lever 

pop safety valve, boiler damper regulator. 

For coal burning hot water boilers: damper regulator, altitude gage, thermometer, relief 

valve. 

For oil burning boilers, the damper regulators are omitted and the following additional 

equipment is usually attached: automatic water feeder, low water cutout, a pressure 

control, and a water temperature control. These are generally furnished by the oil 

burner manufacturer and do not come with the boiler. 

5 What general precautions regarding the boiler should be taken to make 
sure a proposed beating installation will work properly? 

a. Select the right size and type of boiler. 

&. Be sure the combustion space is proper for the type of fuel burned. 

c. Allow sufficient space around the boiler for cleaning. 

d. Secure proper height and area of chimney and connecting breeching. 

e. Clean the boiler thoroughly and provide surface blowoff connections and bottom 
blowoff connections for periodic cleaning after operation is begun. 

/. See that the boiler heating surface is cleaned at regular periods. 

g. Check flue gas temperatures and make a flue gas analysis at least once a month. 

h. Secure information and advice from boiler manufacturer. 

5 What is the average heat transmission rate hi heating boilers hi Btu per 
sq ft of beating surface per hour? 

3500 for coal burning boilers; 4200 for oil burning boilers. 



262 



Chapter 14 

RADIATORS AND GRAVITY CONVECTORS 

Heat Emission of Radiators and Convectors, Types o Radi- 
ators, Output of Radiators, Heating Effect, Heating Up the 
Radiator and Convector, Enclosed Radiators, Convectors, 
Selection, Code Tests, Gravity-Indirect Heating Systems 

THE accepted terms for heating units are: (1) radiators, for direct 
surface heating units, either exposed, enclosed, or shielded, which 
emit a large percentage of their heat by radiation; and (2) connectors, for 
heating units haying a large percentage of extended fin surface and which 
emit heat principally by convection. Convectors are dependent upon 
enclosures to provide the circulation by gravity of large volumes of air. 

HEAT EMISSION OF RADIATORS AND CONVECTORS 

All heating units emit heat by radiation and convection. The resultant 
heat from these processes depends upon whether or not the heating unit is 
exposed or enclosed and upon the contour and surface characteristics of 
the material in the units. 

An exposed radiator emits less than half of its heat by radiation, the 
amount depending upon the size and number of sections. When the 
radiator is enclosed or shielded, radiation is further reduced. The balance 
of the emission is by conduction to the air in contact with the heating 
surface, and the resulting circulation of the air warms by convection. 

A convector emits practically all of its heat by conduction to the air 
surrounding it and this heated air is in turn transmitted by convection to 
the rooms or spaces to be wanned, the heat emitted by radiation being 
negligible. 

TYPES OF RADIATORS 

Present day radiators may be classified as tubular, wall, or window 
types, and are generally made of cast iron. Catalogs showing the many 
designs and patterns available now include a junior size which is more 
compact than the standard unit. 

Pipe Coils 

Pipe coils are assemblies of standard pipe or tubing (1 in. to 2 in.) which 
are used as radiators. In older practice these coils were commonly used 
in factory buildings, but now wall type radiators are most frequently used 
for this service. When coils are used, the miter type assembly is to be 

263 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

preferred as it best cares for expansion in the pipe. Cast manifolds or 
headers, known as branch tees, are available for this construction. 

OUTPUT OF RADIATORS 

The output of a radiator can be measured only by the heat it emits. 
The old standard of comparison used to be square feet of actual surface, 
but since the advance in radiator design and proportions, the surface area 
alone is not a true index of output. (The engineering unit of output is the 
Mb or 1000 Btu.) However, during the period of transition from the old 
to the new, radiators may be referred to in terms of equivalent square feet. 
For steam service this is based on an emission of 240 Btu per hour per 
square foot. 

TABLE 1. VARIATION IN DIMENSIONS AND CATALOG RATINGS OF 
10-SECTiON TUBULAR RADIATORS 



No_rfTuh 


3 


4 


5 


6 


7 














Wiritfl of T^'ftt- Tnp.hea 


4.6-5.1 


6.0-7.0 


8.0-8.9 


9.1-10.4 


11.4-12 8 














L$pgt)i p^f Sftfltirm ^ it Inches 


2.5 


2.5 


2.5 


2.5 


2.5-30 














HEIGHT WITH LEGS INCHES 


HEJ 


LT EMISSION 


EQUIVALENT S 


QUA.RE FEET 




13-14 








20 


25 0-32 5 


16-18 






28.5 




30 0-38 3 


20-21 
22-23 
25-26 
30-32 
36-38 


15.0-17.5 
20.0-21.3 
20.0-26.7 
25.0-30.9 
30.0-36.7 


20.0-22.5 
25 
25.0-27.5 
33.3-35.0 
40.0-42.5 


25.0-31.2 
30.0-33.9 
32.5-39.8 
40.0-48.6 
50.0-56.5 


30 
35 
37.5-40.0 
50 
60 


36.7-45.0 
40.0-45.2 
50.0-53.5 
63.3-62.5 
70.0-75.4 



Output of Tubular Radiators 

^ Table 1 illustrates the difficulty in tabulating tubular radiator outputs 
since there is so much variation in design between the products of the 
different manufacturers. Only on the four-tube and six-tube sizes is there 
any practical agreement in output value. The heat emission values 
appear as square feet but are entirely empirical, being based on the heat 
emission of the radiator and not on the measured surface. 

Output of Wall Radiators 

An^average value of 300 Btu per actual square foot of surface area per 
hour has been found for wall radiators one section high placed with their 
bars vertical. Several recent tests 1 show that this value will be reduced 
from 5 to 10 per cent if the radiator is placed near the ceiling with the bars 
horizontal and in an air temperature exceeding 70 F. When radiators 
are placed near the ceiling, there is usually so noticeable a difference in 
temperature between the floor level and the ceiling that it becomes dif- 
ficult to heat the living zone of a room satisfactorily. 



^University of Illinois, Engineering Experiment Station Bulletin No. 223, p. 30. 

264 



CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS 



Output of Pipe Coils 

The heat emission of pipe coils placed vertically on a wall with the 
pipes horizontal is given in Table 2. This has been developed from avail- 
able data and does not represent definite results of tests. For such coils 
the heat emission varies as the height of the coil. The heat emission of 
each pipe of ceiling coils, placed horizontally, is about 12G Btu, 156 Btu, 
and 175 Btu per linear foot of pipe, respectively, for l-in. t lj^-in., and 
13/2-in. coils. 

TABLE 2. HEAT EMISSION OF PIPE COILS PLACED VERTICALLY ON A WALL (PIPES 
HORIZONTAL) CONTAINING STEAM AT 215 F AND SURROUNDED WITH AIR AT 70 F 

Btu per linear foot of coil per hour (not linear feet of pipe) 



SIZE OF PIPE 



I 



It?. 



\\i IN. 



VA IN. 



Single row 


132 


162 


185 


L s 

Two 


252 


312 


348 


Four _ 


440 


545 


616 


Six. 
Eight. - 


567 
651 


702 
796 


793 
907 


Ten - 
Twelve 


732 
812 


907 
1005 


1020 
1135 



Effect of Paint 

The prime coat of paint on a radiator has little effect on the heat output, 
but the finishing coat of paint does influence the radiation emission. Since 
this is a surface effect, there is no noticeable change in the convection loss. 
Thus, the larger the proportion of direct radiating surface, the greater 
will be the effect of painting on the radiation. Available tests are on old- 
style column type radiators which gave results shown in Table 3. 

TABLE 3. EFFECT OF PAINTING 32-iN. THREE COLUMN, SIX-SECTION 
CAST-IRON RADiATOR a 



RADIATOR 
No. 


FINISH 


AREA 
SQFT 


COEFFICIENT 
or HEAT TRANS. 
BTU 


RELATIVE 
HEATING VALUE 
PER CENT 


1 
2 
3 
4 


Bare iron, foundry finish 
One coat of aluminum bronze... 
Gray paint dipped 


27 
27 
27 
27 


1.77 
1.60 
1.78 
1.76 


100.5 
90.8 
101.1 
100.0 


One coat dull black Pecora paint 



^Comparative Tests of Radiator Finishes, by \V. H. Severns (A.S.H.V.E. TRANSACTIONS, Vol. 33, 
1927, p. 41). 

Effect of Superheated Steam 

Available research data indicate that there is probably a decrease in 
heat transfer rate for a radiator or gravity convector with superheated 
steam in comparison with saturated steam at the same temperature. 
The decrease is probably small for low temperatures of superheats and 
additional tests are necessary with varying degrees of superheat to 
establish accurate comparisons for all types of radiators and convectors 2 . 

s Tests of Radiators with Superheated Steam, by R. C. Carpenter (A.S.H.V.E. TRANSACTIONS, Vol. 7, 
1901, p. 206). 

265 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



HEATING EFFECT 

For several years the heating effect of radiators has been considered by 
engineers in order to use it for the rating of radiators and in the design of 
heating systems. Heating effect is the useful output of a radiator, in the 
comfort zone of a room, as related to the total input of the radiator 3 . 



^CoW room temp m deg F 



01234... 
Net Ib of steam condensed per hour 



5 52 Ib Test R-E2, 5-tube rad 
5 62 Ib Test R-E61, 3-tube rad 
5.42 Ib Test R-E10, 1-tube panel rad 

5.50 Ib Test R-2c, (Bui 223) wall rad 

5678 




2 3 



HEIGHT ABOVE FLOOR IN FEET 

FIG. 1. ROOM TEMPERATURE GRADIENTS AND STEAM CONDENSING RATES FOR FOUR 
TYPES OF CAST-IRON RADIATORS WITH A COMMON TEMPERATURE AT THE 60-lN. LEVEL 

Note that the steam condensations are practically the same for all four radiators when the same air 
temperature of 69 F is maintained at the 60-in. level. avr 



6.68 Ib Test R-E56, 5-tube rad. 
6.48 Ib Test R-E20, 3-tube rad. 
6 12 Ib Test R-E58, 1-tube panel rad. 
55.0 Ib Test R-2c, (Bui. 223} wall rad 
7 8 




HEIGHT ABOVE FLOOR IN FEET 

FIG. 2. ROOM TEMPERATURE GRADIENTS AND STEAM CONDENSING RATES FOR FOUR 
TYPES OF CAST-IRON RADIATORS WITH A COMMON TEMPERATURE AT THE 30-lN LEVEL 

68 plsma^ai^d ^ SoSn^fel *" dftoBlt ^ aU * radiatOre when the sam < ** **<** of 

The results of tests conducted at the University of Illinois are shown in 
*igs. 1 and 2 4 . For the four types of radiators shown, the following; con- 
clusions are given: 



c a. by Dr- Charles Brabbee (A.S.H.V.E. TRANSACTIONS Vol 33 1927 



266 



CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS 



1. The heating effect of a radiator cannot be judged solely by the amount of steam 
condensed within the radiator. 

2. Smaller floor-to-ceiling temperature differentials can be maintained with long, low, 
thin, direct radiators, than is possible with high, direct radiators. 

3. The larger portion of the floor-to-ceiling temperature differential in a room of 
average ceiling height heated with direct radiators occurs between the floor and the 
breathing level. 

4. The comfort level (approximately 2 ft-6 in. above floor) is below the breathing line 
level (approximately 5 ft-0 in. above floor), and temperatures taken at the breathing 
line may not be indicative of the actual heating effect of a radiator in the room. The 
comfort-indicating temperature should be taken below the breathing line level. 

5. High column radiators placed at the sides of window openings do not produce as 
comfortable heating effects as long, low, direct radiators placed beneath window 
openings 5 . 

HEATING UP THE RADIATOR AND CONVECTOR 

The maximum condensation occurs in a heating unit when the steam 
is first turned on 6 . Fig. 3 shows a typical curve for the condensation rate 
in pounds per hour for the time elapsing after steam is turned into a cast- 
iron radiator. The data are from tests on old style column type radiators. 



; i u 

85 

Qu 

t 0.8 



oe. 

UJ 

** OC 








1 


\ 






























/ 


\ 




























i 


/ 




\ 
































V 


\ 




















z 


5n, 






/ 








\l 






















/ 












\ 


















RATE OF CONDENSE 

o c 

K) 4 




/ 












\ 


\ 
















/' 


f 














^v 






























































/ 

































10 20 30 

TIME ELAPSED AFTER STEAM TURNED INTO RADIATOR, MINUTES 



40 



FIG. 3. CHART SHOWING THE STEAM DEMAND RATE FOR HEATING UP A CAST-IRON 
RADIATOR WITH FREE AIR VENTING AND AMPLE STEAM SUPPLY 

In practice the rate of steam supply to the heating unit while heating up 
is frequently retarded by controlled elimination of air through air valves 
or traps. Automatic control valves may also retard the supply of steam. 

ENCLOSED RADIATORS 

The general effect of an enclosure placed about a direct radiator is to 
restrict the air flow, diminish the radiation and, when properly designed, 
improve the heating effect. Recent investigations 7 indicate that in the 
design of the enclosure three things should be considered: 

'Effect of Two Types of Cast-iron Steam Radiators in Room Heating, by A. C. Willard and M. K. 
Fahnestock (.Heating, Piping and Air Conditioning, March, 1930, p. 185). 

*The Cooling and Heating Rates of a Room with Different Types of Steam Radiators and Convectors, 
by A. P. Kratz, M. K. Fahnestock and E. L. Broderick (A.S.H.V.E. JOURNAL SECTION, Heating, Piping 
and Air Conditioning, April, 1937, p. 251). 

'University of Illinois, Engineering Experiment Station Bulletin Nos. 192 and 223, and Investigation of 
Heating Rooms with Direct Steam Radiators Equipped with Enclosures and Shields, by A. C. Willard, 
A. P. Kratz, M. K. Fahnestock and S. Konzo (A.S.H.V.E. TRANSACTIONS, Vol. 35, 1929, p. 77). 

267 



HEATING VENTIIIATING AIR CONDITIONING GUIDE 1938 



1. There should be better distribution of the heat below the breathing line level to 
produce greater heating comfort and lowered ceiling temperatures. 

2. The lessened steam consumption may not materially change the radiator heating 
performance. 

3. The enclosed radiator may inadequately heat the space. 

A comparison between a bare or exposed radiator (A) and the same 
radiator with a well-designed enclosure (j5), with a poorly-designed 
enclosure (C), and with a cloth cover (D) will illustrate the relative 
heating effects. In Fig. 4 the curve (B) reveals that the enclosed radiator 
used less steam than the exposed radiator, but gave a satisfactory heating 
performance. A well-designed shield placed over a radiator gives about 
the same heating effect. Curve (C) shows the unsatisfactory effects 
produced by improperly designed enclosures. Curve (D) shows that the 



TEMPERATURE IN DEG FAHR 
S S 3 S 


















^^ 














A-, 
^ 


^j 


_ 


'^ 








8 

is' 


^ 


^'' 












^ 


? 

3t 


&' 
^ 


< 










^ 


XX 


>- 




Radiator 


Steam consumption 




Lb per hr 


Per cent 


V 


/ 






A 
B 
C 
D 


5.44 
4.71 
4.50 
4.59 


100 
86.6 
82.7 
84.4 





































2468 
HEIGHT ABOVE FLOOR fN FEET 



10 
FIG. 4. STEAM CONSUMPTION OF EXPOSED AND CONCEALED RADIATORS 



effect of a cloth cover extending downward 6 in. from the top of the 
radiator was to make the performance unsatisfactory and inadequate. 
Practically all commercial enclosures and shields for use on direct 
radiators are equipped with water pans for the purpose of adding moisture 
to the air in the room. Tests 8 show that an average evaporative rate of 
about 0.235 Ib per square foot of water surface per hour may be obtained 
from such pans, when the radiator is steam hot and the relative humidity 
in the room is between 25 and 40 per cent. This source of supply of 
moisture alone is not adequate to maintain a relative humidity above 
25 per cent on a zero day. 

CONVECTORS OR CONCEALED HEATERS 

Although any standard radiator may be concealed in a cabinet or 
other enclosure so that the greater percentage of heat is conveyed to the 

University of Illinois, Engineering Experiment Station Bulletin No. 230, p. 20. 

268 



CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS 



room by convection thereby resulting in a form of gravity con vector, 
generally better results are obtained with specially designed units which 
permit a free circulation of a larger volume of air at moderate tempera- 
tures. Since air stratifies according to temperature, moderate delivery 
temperatures at the outlet of the enclosure reduce the temperature dif- 
ferential between the floor and ceiling and accordingly accomplish the 
desired heating effect in the living zone. 

Fig. 5 shows a typical built-in convectpr. The heating element con- 
sisting of a large percentage of fin surface is usually shallow in depth and 




SECTION 
FIG. 5. TYPICAL CONCEALED CONVECTOR USING SPECIALLY DESIGNED HEATING UNIT 

placed low in the enclosure in order to produce maximum chimney effect 
in the enclosure. The air enters the enclosure near the floor line just 
below the heating element, is moderately heated in passing through the 
core and delivered to the room through an opening near the top of en- 
closure. Since the air can only enter the enclosure at the floor line, the 
cooler air in the room which always lies at this level, is constantly being 
withdrawn and replaced by the warmer air. This air movement accom- 
plishes the desired reduction in temperature differentials and assures 
maximum comfort in the living zone. 

The Convector Manufacturers Association has adopted the A.S.H.V.E. 
Standard 9 in the formulation of its ratings and has compiled a tentative 



A.S.H.V.E. Standard Code for Testing and Rating Concealed Gravity Type Radiation (Steam), 
(A.S.H.V.E. TRANSACTIONS, Vol. 37. 1931. p. 367); (Hot Water). (A.S.H.V.E. TRANSACTIONS, Vol. 3<), 
1933, p. 237). 

269 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

standard of heating effect allowances for various enclosure heights to be 
included in the ratings by its members. 

All published ratings bearing the title C.M.C. Ratings (Convector Manu- 
facturers Certified Ratings) indicate that the convectors have been tested 
in accordance with the A.S.H.V.E. Code by an impartial and disinterested 
laboratory and that the ratings have been approved by the Standardiza- 
tion Committee of the Convector Manufacturers Association. 

Concealed heaters or cpnvectors are generally sold as completely 
built-in units. The enclosing cabinet should be designed with suitable 
air inlet and outlet grilles to give the heating element its best performance. 
Tables of capacities are catalogued for various lengths, depths and heights, 
and combinations are available in several styles for installations, such as 
the wall-hung type, free-standing floor type, recess type set flush with wall 
or offset, and the completely concealed type. Most of these types may be 
arranged with a top outlet grille in a plane parallel with the floor, although 
the front outlet is practically standard. In cases where enclosures are to 
be used but are not furnished by the heater manufacturer, it is important 
that the proportions of the cabinet and the grilles be so designed that they 
will not impair the performance of the assembled convector. It is impor- 
tant that the enclosure or housing for the convector fit as snugly as pos- 
sible so that the air to be heated must pass through the convector and 
cannot be by-passed in the enclosure. 

The output of a convector, for any given length and depth, is a variable 
of the height. Published ratings are generally given in terms of equiva- 
lent square feet, corrected for heating effect. However, an extended 
surface heating unit is entirely different structurally and physically from 
a direct radiator and, since it has no area measurement corresponding to 
the heating surface of a radiator, many engineers believe that the per- 
formance of convectors should be stated in Btu's. For steam convectors, 
as for radiators, 240 Btu per hour may be taken as an equivalent square 
foot of radiation. 

RADIATOR AND CONVECTOH SELECTION 

Since the capacity of a radiator varies as the 1.3 power and a convector 10 
as the 1.5 power of the temperature difference between the inside of 
radiator and surrounding air it is obvious that for other than 70 F room 
temperatures the heat emission will be other than 240 Btu per square foot 
of rating. Therefore in selecting the size of radiator or convector to be 
used it is necessary to correct for this difference. Table 4 shows factors by 
which radiation requirements, as determined by dividing heat load by 
240, shall be multiplied to obtain proper radiator or convector sizes from 
published rating tables for room temperatures ranging between 50 and 
80 F as well as for steam or water temperatures from 150 to 300 F. For 
other room and heating medium temperatures the factor is determined by 
the following formulae: 

For radiators: 

C s - /215 ~ 70V ' 3 



"Factors Affecting the Heat Output of Convectors, by A. P. Kratz, M. K. Fahnestock, and E. L. Brod- 
erick (A.S.H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 443). 

270 



CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS 



For con vectors: 



where 



C s = correction factor. 
/ a steam temperature, degrees Fahrenheit. 
t T room temperature, degrees Fahrenheit, 
/i = average inlet air temperature, degrees Fahrenheit. 

TABLE 4. CORRECTION FACTORS FOR DIRECT CAST-IRON RADIATORS AN*I> 
Cox VECTOR HEATERS* 



STEAM ., FACTORS FOR DIRECT 
PRESS. , bTEAM CAST-IRON RADIATOR FACTORS FOR ( UVVLIT JKS 


AFFHOi. . YVxTEH ' R *P P ' T ,. 4 . ! T^..^^^..^. -^ t' 


fiagp ' Ahh. TEMP. 








Vacuum Lb p<-r ' F ' 








In. Hg ! Sqlri. j 


80 , 75 70 65 


60 


55 , 50 80 75 


70 , 65 GO 


J3 


5U 


22A , 3.7 | 150 


2.58 2.36 , 2.17 2.00 


1.86 


1.73 ] 1.62 ; 3.11 2.83 


2.57 2.35 


2.15 


1.98 


1.8* 


20.3 4.7 ! 160 


2.17 


2.00 | 1.86 


1.73 


1.62 


1.52 1.44 I! 2.57 


2.35 


2.15 1.98 


1.84 


1.71 


1.59 


17.7 , 6.0 j 170 


1.86 


1.73 


1.62 


1.52 


1.44 


L35 i 1.28 ;{ 2.15 


1.98 


1.84 i 1.71 


1.59 


1.49 


1.40 


14.6 7.5 . 180 


1.62 ' 1.52 1.44 


1.35 


1.28 


1.21 1.15 | 1.84 


1.71 


1.59 i 1.49 


1.40 


1.32 


1.24 


10.9 9.3 ! 190 


1.44 1.35 , 1.28 


1.21 


1.15 


1.10 


1.05 i. 1.59 


1.49 


1.40 i 1.32 


1.24 


117 


1.11 


6.5 ! 11.5 | 200 


1.28 


1.21 


1.15 ; 1.10 


1.05 


1.00 


0.96 i 1.40 


1.32 


1.24 ; 1.17 


1.11 


1.05 


1.00 


LbperSqln.' I 




:i 




! 








1 15.6 i 215 1.10 ! 1.05 i 1 00 


0.96 


0.92 ' 0.88 


O.S5 I- 1.17 1.11 


1.05 i 1.00 


095 


0.91 


087 


6 '21 1 230 ! 0.96 


0.92 


0.88 


0.85 


0.81 0.78 


0.76 j 1.00 0.95 


0.91 | 0.87 


0.83 


0.79 


0.76 


15 , 30 250 j 0.81 


0.78 


0.76 0.73 


0.70 


0.68 


0.66 'I 0.83 


0.79 


0.76 , 0.73 ; 70 


0.68 


005 


27 : 42 i 270 70 


068 


0.66 0.64 


0.62 


0.60 


0.58 ;| 0.70 


0.68 


0.65 I 0.63 j 0.60 


0.58 


0.56 


52 i 67 ! 300 1 0.58 


0.57 


0.55 


0.53 


0.52 


0.51 


0.49:i 0.56 0.54 


0.53 i 0.51 ! 0.49 j 0.4* 


0.47 



To determine the heater size for a given space, divide the heat loss in Btu per hour by 240 and multiply 
the result by the proper factor from the above table. 

To determine the heating capacity of a heater at other than standard conditions, divide the heating 
capacity at standard conditions by the proper factor from the above table. 

CODE TEST FOR RADIATORS AND CONVECTORS 

As previously indicated, the output of radiators and convectors is still 
designated by the terms of older practice, but this is gradually giving place 
to an engineering method of designating heat emission. The A.S.H.V.E. 
has adopted the following standards : Code for Testing Radiators (1927) ; 
Codes for Testing and Rating Concealed Gravity Type Radiation (Steam, 
1932, and Hot Water, 1933). 

For steam services the actual condensation weight is taken without any 
allowance for heating effect ; for hot water services the weight of circulated 
water is used without allowance for heating effect* In all cases the total 
heat transmission varies as the 1.3 power for radiators 11 and the 1.5 
power for convectors 12 of the temperature difference between that inside 
the radiator and the air in the room, and is expressed in Btu or Mb 
per hour. 

Standard test conditions specify either a steam pressure of 1 Ib gage 
(215 F), or hot water at 170 F and a room temperature of 70 F for radi- 
ators, or an inlet air temperature of 65 F for convectors. The heating 
capacity of a steam radiator or steam converter is determined as follows: 

f/t = WJitt W 



"Loc. Cit. Note 9. 

Loc. Cit. Notes 9 and 10. 



271 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

where 

Ht = Btu per hour under test conditions. 
W s ~ condensation in pounds per hour, 
//fg = latent heat in Btu per pound. 

Ht may be converted to standard conditions of code ratings by using 
the proper correction factor from the following formulae : 
For radiators: 

r - ( 21 * - 70 V- 3 - ( 1 M__V' 3 t*\ 

L * ~ \T a -TrJ ~ \T S - T T ) W 

For con vectors: 

Cs . (=)" = (T^)" 0) 

The output under standard conditions will be: 

H a * C s Ht W 

where 

C s = correction factor. 

r s = steam temperature during test, degrees Fahrenheit. 

T T = room temperature during test, degrees Fahrenheit. 

T{ = inlet air temperature during test, degrees Fahrenheit. 

H s = heat emission rating under standard conditions, Btu per hour. 

Similarly, for hot water converters, the output under test conditions may 
be determined as follows: 



H = w (B! - 2 ) ^p (5) 

where 

H = Btu per hour under test conditions. 
W = pounds of water handled during test. 

81 average temperature of inlet water, degrees Fahrenheit. 

8 2 = average temperature of outlet water, degrees Fahrenheit. 
t - duration of test, seconds. 

To convert test results to standard conditions, the following correction 
factor is used: 

170-65 \i- / 105 

(6) 



* 1 



It has been shown that when the exponent 1.5 is used the range of error 
is less than 3 per cent 13 for convectors. 

GRAVITY-INDIRECT HEATING SYSTEMS 14 

The heating units for this system are usually of the extended surface 
type for steam or hot water, and are installed about as shown in Fig. 6. 
The temperature and volume of the air leaving the register must be great 

1! Loc. Cit. Note 10. 

"For further information on this subject see A.S.H.V.E. Code of Minimum Requirements for the Heating 
and Ventilation of Buildings (edition of 1929) and Mechanical Equipment of Buildings, by Harding and 
Willard. Vol. 1, second edition, 1929. 

272 



CHAPTER 14. RADIATORS AND GRAVITY CONVECTORS 

enough so that in cooling to room temperature the heat available will jus 
equal the heat loss during the same time. In cases where ventilation is < 
requirement, the air volume needed may become so large that the enterini 
air temperature will be but slightly above the room temperature. T< 
establish and maintain a constant heat flow, provision must be made fo 
removing the air in the room, after it has cooled to the desired room tern 
perature, by a system of vent flues or ducts. As the air flow is maintainec 



Supports'hung from joist or floor above 




Felt Strips 
at Edge" 



Recircutatmg Duct- 

FIG. 6. GRAVITY-INDIRECT HEATING SYSTEM* 

See Mechanical Equipment of Buildings, by Harding and Willard, Vol. I, second edition, 1929. 

by natural draft and this gravity head is very slight, it is necessary to 
make all ducts as short as possible, especially the runs from the heating 
units to the base of the vertical warm air flues. Gravity-indirect arrange- 
ments, such as illustrated in Fig. 6, are not to be generally recommended 
for hot water systems unless the water temperature can be maintained at 
a reasonably high temperature and rapid circulation of the water can be 
had. 



PROBLEMS IN PRACTICE 

* he effect on the heat output of a wall radiator when installed on 
the ceiling of a room? 

Because the temperature differential is increased between the floor level and the ceiling 
when a wall radiator is placed near the ceiling, the heat output may be decreased from 
5 to 10 per cent. Under such circumstances it becomes difficult to heat the living zone 
of a room satisfactorily. s 

273 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

2 What are the principal differences between a radiator and a convector? 

A radiator is commonly thought of as a commercial heating unit having a maximum 
amount of direct heating surface, whereas a convector is a heating device in which the 
extended or secondary surface may be several times that of the prime surface and which 
is specially designed to utilize to the fullest extent the convection principal of heating. 
The radiator ordinarily has vertical tubular chambers for the heating medium but most 
converters have horizontal tubular chambers to which fins are attached so as to form 
vertical flues for the passage of air. While radiators are either exposed, enclosed, or 
shielded, convectors are concealed by means of a tight-fitting enclosure. Radiators are 
commonly made of cast iron but convectors may be made of a combination of metals, 
such as copper and brass, or copper and aluminum, as well as entirely of cast iron. 

3 How did the term heating effect come into use? 

It has been found that a room requiring a radiator of a certain determined capacity 
could under certain conditions be properly heated, with less temperature gradient be- 
tween^ floor and ceiling and with less steam condensation, by the same radiator or by one 
of a different design having the same commercially rated capacity. This resulted in the 
use of the term heating effect to apply to the useful heat output of a radiator, in the com- 
fort zone of a room, as related to the total input to the radiator. 

4 Is it necessary to make any allowance for the performance of a convector 
because it is enclosed? 

No. The commercial ratings of convectors have been determined by testing the con- 
vectors in proper enclosures with grilles in place just as they should be installed for 
ordinary service. 

5 On what basis are the capacities of convectors published? 

Published ratings of convectors are expressed in equivalent square feet of direct cast 
iron radiation. Some manufacturers have increased their ratings by as much as 30 per 
cent to allow for a supposed improved heating effect. Tests indicate that the credit to 
be given heating effect is, in all cases, probably less than 10 per cent, and in many cases 
negligible. 

6 How are fins of convectors attached to the tubes or prime surface? 

Tubes or a solid core may be forced through piercings in the fins under pressure or the 
tubes may be expanded into the holes through the fins. In addition a metallic bonding 
agent is sometimes used to insure permanent contact. 

7 What is the procedure in selecting a convector when the required amount 
of radiation is known? 

First the limiting factor or factors of the enclosure must be determined so the available 
size of the wall recess can be found. Manufacturers' catalogs show capacities of con- 
vectors of each standard length and depth with varying enclosure heights. From these 
capacity tables, the proper convector of the required capacity can be selected for the 
available wall recess. If all three dimensions of the wall recess are insufficient to accom- 
modate a convector of the required capacity, the available height and length can be 
maintained, but greater depth can be obtained by using a partially recessed enclosure. 

8 Given a room to be heated to 80 F with outside temperature at F, 
assume the heat loss under these conditions to be 10,000 Btu per hour. Deter- 
mine the size of the steam radiator to be installed. 

A square foot of radiation is equivalent to a heat emission of 240 Btu per hour under 
Sta 2^ d conditions of steam at one pound gage pressure (215 F) and surrounding air 
at 70 F. With surrounding air at 80 F, the heat emission from a radiator will be less. 
Under these conditions, the heat emission will not be 240 Btu per square foot of catalog 
rating per Jiour, but 240 C s . 



- ( 
" V 



~ ft V'* - /^ 215 - SON 1 - 3 n 
215 - 70} ~ V215 - 70 J " ' 912 ' 



and 240 C 8 - 240 X 0.912 - 218.5 Btu. Therefore, the size of the radiator to be 
selected shall have a catalog rating of 10,000 divided by 218.5 or 45.8 sq ft. 



274 



Chapter 15 

STEAM HEATING SYSTEMS 

Gravity and Mechanical Return, Gravity One-Pipe Air- Vent 
System, Gravity Two-Pipe Air- Vent System, One-Pipe Vapor 
System, Two-Pipe Vapor System, Atmospheric System, 
Vacuum System, Sub-Atmospheric System, Orifice System, 
Zone Control, Auxiliary Conditioning Unit, Condensation 
Return Pumps, Vacuum Pumps, Traps 

THE essential features of the common type of steam heating systems 
are described in this chapter. They may be classified according to the 
piping arrangement, the accessories used, the method of returning the con- 
densate to the boiler, the method of expelling air from the system, or the 
type of control employed. Information concerning the design and layout 
of steam heating systems will be found in Chapter 16. 

GRAVITY AND MECHANICAL RETURN 

In gravity systems the condensate is returned to the boiler by gravity 
due to the static head of water in the return mains. The elevation of the 
boiler water line must consequently be sufficiently below the lowest 
heating units and steam main and dry return mains to permit the return 
of condensate by gravity. The water line difference 1 must be sufficient to 
overcome the maximum pressure drop in the system and, when radiator 
and drip traps are used as in two-pipe vapor systems, the operating 
pressure of the boiler. The condensing return of the radiation will 
increase the required water line difference and is especially important 
where the radiation is a type having a high condensing rate. This applies 
only to closed circuit systems, where the condensation is returned to the 
boiler. If the condensation is wasted, no water line difference is required, 
but other conditions are introduced which warrant the use of an appro- 
priate mechanical system in preference to wasting the condensate. 

In mechanical systems the condensate flows to a receiver and is then 
forced into the boiler against the boiler pressure. The lowest parts of the 
supply side of the system must be kept sufficiently above the water line 
of the receiver to insure adequate drainage of water from the system, but 
the relative elevation of the boiler water line is unimportant in such cases 



J The icatcr line difference is the distance between the water line of the boiler and the level of the water 
in the dry or wet return main. (See Fig. 4.) 

275 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



except that the head on the pump or trap discharge becomes greater as 
the height of the boiler water line above the trap or pump increases. 

There are three general types of mechanical returns in common use, 
namely, (1) the mechanical return trap, (2) the condensation return 
pump, and (3) the vacuum return pump. Further information on pumps 
and traps will be presented later in this chapter. 

GRAVITY ONEPIPE AIR-VENT SYSTEM 

In the gravity one-pipe air- vent system each radiator has but a single 
connection through which steam must enter and condensation must 
return in the opposite direction. Each radiator has an individual air 
valve. 

Up-Feed Gravity One-Pipe Air-Vent System 

This system is the most common of all methods of steam heating, 
especially for small size installations, due largely to its low cost of instal- 



Air valve 




Hartford 
return - 
connection 




Riser dripped 
Boiler water line^ 




Wet return^ 
FIG. 1. TYPICAL UP-FEED GRAVITY ONE-PIPE AIR- VENT SYSTEM 

lation and its simplicity. Where the size of the system is moderate or 
largest cannot be assumed that these systems will be lower in cost than 
two-pipe systems using steam traps. In some instances it has been found 
that the cost of one-pipe systems under these conditions is greater owing 
to the higher cost of labor and materials due to the larger pipe sizes. As 
will be seen from Fig. 1, the steam piping rises to a point as high as possible 
at the boiler and pitches downward from this location until the far end of 
the main or mains is reached. At the far ends drips are taken off at the 
low points of the steam mains, are water-sealed below the boiler water 
line, and then brought back to the boiler in a wet return. Single pipe risers 



276 



CHAPTER 15. STEAM HEATING SYSTEMS 



are branched off the main or mains to feed the radiators, the steam passing 
up the riser and the condensation flowing down it. The steam and con- 
densation flow in opposite directions in the riser but after the condensa- 
tion enters the steam main it flows in the same direction as the steam and 
is disposed of through the drip connection at the end of the main. In 
buildings of several stories, it is customary to drip the heel of each riser 
separately, whereas in one- or two-story buildings this is not necessary. 
Both types of branches and risers are shown in Fig. 1. 

Rapid elimination of air and condensation from the steam piping is 
essential to the successful operation of this system. It is therefore 
desirable that the venting and dripping of the steam main in long runs be 
made at several intermediate points where the steam main may again be 
brought to a higher elevation. 

It is desirable to install the air-vent valves on the steam main about a 
foot ahead of the drips, as is indicated in Fig. 1 to prevent possible damage 
to the mechanism of the air- vent valve by water, in case the valves are 
installed directly above the drips. 

Horizontal branches to radiators and risers should be pitched at least 
J^ in. in 10 ft downward toward the riser or vertical pipe, and the hori- 



Up to radiator or riser- 
- Pitch 




Steam main 

5 ft approximately 




FIG. 2. TYPICAL STEAM RUNOUT WHERE FIG. 3. TYPICAL STEAM RUNOUT WHERE 
RISERS ARE NOT DRIPPED RISERS ARE DRIPPED 

zontal branches from the steam main should be graded at least this 
amount toward the main, except where the heel of the riser is dripped, in 
which case the branch should pitch down toward the riser drip (Figs. 2 
and 3). The return line, if wet, may be run without pitch or may be 
pitched in either direction, but if it is necessary to carry the return main 
overhead for any distance before dropping, the return should slope down- 
ward with the flow. It is desirable to install the wet return pipe with a 
pitch so that the system may be drained to prevent freezing in case the 
building remains unoccupied for a considerable length of time. 

The radiator valves may be of the angle-globe or gate type. They 
should not be of the straight-globe type because the damming effect of the 
raised valve seat interferes with the flow of condensation through the 
valve. Graduated valves cannot be used, as the steam valves on this 
system must be fully open or closed to prevent the radiators filling with 
water. Air valves may be manual or automatic, with or without a check 
to prevent the re-entrance of expelled air. Usually the automatic type is 
installed. An objection to one-pipe steam systems is that the heat is all 
on or all off, with no intermediate position possible. However, intelligent 

277 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

use of the on-and-off method of manual control gives reasonably satis- 
factory results. Improved systems and devices are now available which 
make it possible to obtain a modulating effect from one-pipe gravitv 
heating systems. J 

It is important that the lowest points of the steam mains and heating 
units be kept sufficiently above the water line of the boiler to prevent 



Boiler steam pressure 

u-x-ii; 



Steam pressure at 
end of main 

Return water 




/Floor 



FIG. 4. DIFFERENCE IN STEAM PRESSURE 

ON WATER IN BOILER AND AT END 

OF STEAM MAIN 



Supply riser- 




^ 



Supply main 



^Drop riser 
Air valve 




Hartford 

return 

connection 




Mr valve 



Air vent 




"Air valve 




return 



FIG. 5. TYPICAL DOWN-FEED GRAVITY ONE-PIPE AIR- VENT SYSTEM 

18in - is suffident tat construction limitations foe- 



278 



CHAPTER 15. STEAM HEATING SYSTEMS 



.usually about 3 in. unless the pipes are small or full of sediment , and it will rise still 
farther it a check valve is installed in the return so as to obtain sufficient head to lift the 
tongue of the check (usually 4 in. will be necessary /. 

If a one-pipe steam system is designed, for example, for a total pressure drop of l /$ Ib, 
and utilizes an Undenmters' Loop* instead of a check valve on the return, the rise in the 
water level at the far end of the return due to the difference in steam pressure would be 
Ys of 28 in., or 3H in. Adding 3 in. to this for the flow through the return main and 6 in. 
as a factor of safety gives 12J^ in. as the distance the bottom of the lowest part of the 
steam main and all heating units must be above the boiler water line. The same system 
however, installed and sized for a total pressure drop of J/ Ib, and with a check in the 
return, would require 1 A of 2S in., or 14 in., for the difference in steam pressure, 3 in. for 
the flow through the return, 4 in. to operate the check, and 6 in. for a factor of safety, 
making a total of 27 in. as the required distance. Higher pressure drops would increase 
the distance accordingly. 

Down-Feed Gravity One-Pipe Air-Vent System 

In the overhead down-feed gravity one-pipe air- vent system there is no 
change over the up-feed system in the radiators, the radiator valves, the 
air valves, or the radiator runouts as far back as the risers. Beyond this 




Pitch 




Steam drop to radiators | ^ Steam drop to radiators 



FIG. 6. STEAM RUNOUTS DRIPPING MAIN FIG. 7. STEAM RUNOUTS WITH MAIN 

DRIPPED AT END ONLY 

* point there are basic differences. The steam is taken from the boiler and 
carried to the top of the building as near the boiler as possible (Fig. 5). 
If the run to the main riser is long, or if the riser extends several stories in 
order to reach the top, the bottom of the riser should be dripped into the 
wet return. The horizontal main is taken off the top of the riser and 
grades down from the riser toward all of the drops, each drop taking its 
share of the main condensation (Fig. 6), or all of the drops except the last 
may be taken from the top of the main (Fig. 7), the last drop being from 
the bottom and serving as a drain for the entire main. As the overhead 
main does not carry any condensation from the radiators it is immaterial 
which method is used. The air vent shown on the main just before the 
last drop (Fig. 5) may be placed at this point or it may be located at the 
bottom of the drop under the last radiator connection and sufficiently 
above the water line of the boiler to prevent flooding. 

GRAVITY TWO-PIPE AIR-VENT SYSTEM 

The gravity two-pipe system is now considered obsolete although many 
of these systems are still in use in older buildings. Separate supply and 
return mains and connections are required for each heating unit; air 
valves are installed on the heating units and mains; hand valves are 
installed on the returns. 



*See discussion of piping details in Chapter 16. 

279 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Up-Feed Gravity Two-Pipe System 

This system (Fig. 8) has a steam and a return connection to each 
radiator. The radiator valves for steam, return, and air are the same as 
those described for the gravity one-pipe air-vent system. The steam 
main is run and pitched in the same manner as in the one-pipe system, 
but the returns from each radiator are connected into a separate return 
line system which has its risers carried down and joined to a wet return 
line under the boiler water line level. Where the return has to be kept 
high to function as a dry return, it is advisable to connect the return 
risers to the dry return main through water seals about 36 in. deep, as 



Air valve 



Hartford 

return 

connection 



Wet return 




FIG. 8. TYPICAL UP-FEED GRAVITY Two- PIPE AIR- VENT SYSTEM 



shown in Fig. 9, to prevent steam from one riser entering another and 
closing the air valves on the nearest radiators. 

Down-Feed Gravity Two-Pipe System 

The steam main in the down-feed system is carried to the top of the 
building, and the piping of the steam side is arranged practically as in the 
down-feed one-pipe gravity system. The drips at the bottoms of the 
steam drops and the runouts to the radiators are similar to those shown 
in Fig. 8 for the up-feed ^gravity two-pipe system. On the return side of 
the system, the piping is arranged in exactly the same manner as the 
up-feed gravity two-pipe system. 

ONE-PIPE VAPOR SYSTEM 

A vapor system is one which operates under pressures at or near 
atmospheric and which returns the condensation to the boiler by gravity. 
The piping arrangement of a one-pipe vapor system is similar to that of 

280 



CHAPTER 15. STEAM HEATING SYSTEMS 



the gravity one-pipe steam system; in fact, one-pipe gravity installations 
may readily be changed to one-pipe vapor systems by making a few 
simple alterations. The steam radiator valve is a plug cock which when 
opened gives a free and unobstructed passageway for water. The auto- 
matic air valve is of special design to permit the ready release of air from 
the radiator and to prevent the return of the air after it is expelled. The 
air valves on the main are a quick relief type, and the whole system is 
designed to operate on a few ounces of pressure. 

TWO-PIPE VAPOR SYSTEM 

Two-pipe vapor systems may be classified as (1) dosed systems con- 
sisting of those which have a device to prevent the return of air after it is 
once expelled from the system, and which can operate at sub-atmospheric 
pressures for a period of four to eight hours depending upon the tightness 
of the system and rate of firing, and (2) open systems consisting of those 




FIG. 9. METHOD OF CONNECTING TWO-PIPE 
GRAVITY RETURNS TO DRY RETURN MAIN 

which have the return line constantly open to the atmosphere without a 
check or- other device to prevent the return of air, and which operate at a 
few ounces above atmospheric pressure. The open systems have the 
disadvantage of not holding heat when the rate of steam generation is 
diminishing. 

Under the first classification the essentials are packless graduated 
valves on the^ radiators, thermostatic return traps on the returns, and 
traps on all drips unless they are water sealed. Such a system, illustrated 
in Fig. 10, should be equipped with an automatic return trap to prevent 
the water from backing out of the boiler. In this up-feed arrangement 
the supply piping is carried to a high point directly at the boiler and is 
graded down toward the end or ends of the supply main, each supply 
main being dripped at the end into the wet return or carried back to a 
point near the boiler where it drops down below the boiler water line and 
becomes a wet return. From this main, runouts are branched off to feed 
risers or radiators above, these being graded back toward the steam main 
if they are not dripped at the bottom of the riser, or toward the riser if 
the riser heel is dripped. Both conditions are illustrated in Figs. 2 and 3. 

Return risers are connected to each radiator on its return end through 

281 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



thermostatic traps. Their bottoms are connected to the return main 
through runouts which slope toward the main. The return main itself is 
sloped back toward the boiler if it is carried overhead; if run wet, the 
slope may be neglected, although it is desirably to slope the pipe so that 
the system may be drained. An air vent is installed at the point at 
which the return main drops below the water line. In the simplest cases 
this vent consists of a %-in. pipe with a check valve opening outward, but 
certain systems employ special patented forms of vent valves^ designed 
to allow the air readily to pass out of the system and to prevent its ^ return. 
A check valve is inserted in the return main at a point near the boiler and 
a vertical pipe is run up into the bottom of the return trap, which usually 
is located with the bottom about 18 in. above the boiler water line. Some 
traps are constructed so that they will operate when they are installed 



Trap N 



Trap. 



Supply main 



rap 






Hartford 

return 

connection 





ir eliminating and 

pressure equalizing . 

device-See note below* | 

Boiler water line--' 3 ' ' 



Wet return^ 




FIG. 10. TYPICAL UP-FEED VAPOR SYSTEM WITH AUTOMATIC RETURN TRAP* 

"Proper piping connections are essential with special appliances for pressure equalizing and air elimination. 

with their bottom as close as 8 in. above the boiler water line. On the 
other side of this connection a second check valve is installed in the main 
return just before it enters the boiler (Fig. 11). 

Down-Feed Two-Pipe Vapor System 

In the down-feed two-pipe vapor system the steam is carried to the top 
of the building, the top of the vertical riser constituting the high point of 
the system, and the horizontal supply main is sloped down from this 
location to the far ends of each branch. The branches are taken off the 
main from the bottom or at a 45-deg angle downward, with the runouts 
sloped toward the drops (Fig. 6). Thus each branch from the main forms 
a drip and no accumulation of water is carried down any one drop. 
Another method of running the steam main, which is not considered as 
satisfactory but which is practical, is to take the branches off the top of 

282 



CHAPTER 15. STEAM HEATING SYSTEMS 



the main (Fig. 7) and to drip the end of the main through the last riser, as 
illustrated in the down-feed one-pipe system detail shown in Fig. 6. If 
this is done, the pipe drop at the end or ends of the mains should be 
enlarged one pipe size to provide capacity for this concentration of the 
main drip. 

The steam drops are carried down through the building with suitable 
reductions as the various radiator connections are taken off until the 
lowest radiator runout is reached. If the drop is only two or three stories 
high, the portion feeding the bottom radiator should be increased one 
pipe size to provide for draining the riser, and if the drop is over three 
stories high it is well to increase the portion feeding the two lowest radi- 
ators one or two pipe sizes, especially if the two lowest radiators are small 

Air vent and check 
Check 

nt= 

From steam main 




Boiler water 
line 



FIG. 11. TYPICAL CONNECTIONS FOR AUTOMATIC RETURN TRAP 

and the normal size of drop required is 1 in. or less. The bottom of the 
steam drops should terminate with a dirt pocket above which a drip trap 
connection is located, as shown in Fig. 12. The returns on a down-feed 
vapor system are the same as on an up-feed system except that every 
steam drop must have a drip at the bottom connected either into the 
return through a trap or into a separate water-sealed drip line below the 
boiler water line, as illustrated in Fig. 10, in which case the thermostatic 
traps may be omitted. The runouts to the radiators and the radiator 
connections of the down-feed system are the same as those of the up-feed 
system already described. 

ATMOSPHERIC SYSTEM 

The distinguishing features of the atmospheric system are gravity 

283 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



return to the boiler or to waste, graduated or ordinary radiator valves, no 
automatic air valves on the radiators, thermostatic traps on the radiator 
returns, and the venting of all air from the system by means of pipes open 
to the atmosphere. The returns are open to the atmosphere at all times, 
usually by extending the return risers to the top of the building where 
they are either connected together in groups and carried through the roof 
or extended through the roof individually. Atmospheric systems, either 
up-feed or down-feed, are often used where the condensation is not 
returned to the boiler, as in heating systems supplied by high pressure 
steam through pressure-reducing valves at locations far from the boilers. 
The returns may be delivered back to the boiler, if desired, by condensa- 
tion return pumps which are vented to the atmosphere. The return lines 
in such systems are simply gravity waste lines in which the condensation 
flows entirely by gravity and is not aided by any pressure difference 



Bottom of 
steam drop 



Drip trap 



Dirt pocke 




Graduated valve 



x Floor / 



V//////////S 



-Connected to dry return 
(where connected to wet 
return, drip trap may 
be omitted) 

FIG. 12. DETAIL OF DRIP CONNECTIONS AT BOTTOM OF DOWN-FEED STEAM DROP 



Atmospheric systems contemplate maintaining a practically constant 
pressure in the steam pipe and atmospheric pressure in the return pipe. 
When graduated steam valves are provided, they enable the occupant of 
a room to vary the flow area to the radiator so as to obtain a greater or 
lesser heating effect. 

The steam side may be run as that for either up-feed or down-feed 
two-pipe vapor systems, as the conditions require, and the radiator con- 
nections are the same as for vapor systems in that they have graduated 
valves on the radiator supply ends and thermostatic traps on the radiator 
return ends. All drips from the supply main and the steam side of the 
system must pass through thermostatic drip traps before entering the 
return system where only atmospheric pressure exists. Fig. 13 illustrates 
a typical scheme of piping used on atmospheric systems. Such systems 
do not maintain heat in the radiators under declining fires. As the 
steam supply diminishes, air from the atmosphere re-enters through the 
open vent pipe retarding the inflow of steam and cooling the radiator. 

284 



CHAPTER 15. STEAM HEATING SYSTEMS 



VACUUM SYSTEM 

In ^the vacuum system, a vacuum is maintained in the return line 
practically at all times but no vacuum is carried on the steam side, and the 
usual accessories include graduated valves on the radiator supply and 
thermostatic traps on the radiator return. The air is expelled from the 
system by a vacuum pump and all drips must pass through thermostatic 
traps before connecting to the return side of the system. 

These systems are often fed from high pressure steam mains through 
pressure-reducing valves but they may be fed direct from a low-pressure 
steam heating boiler as shown in Fig. 14, in which a typical up-feed 
vacuum system is illustrated. The supply main slopes down in the 
direction of flow; the runouts pitch down toward the riser if the riser is 
dripped (Fig. 3) or up toward the riser if the riser is not dripped (Fig. 2) ; 
both conditions are indicated in Fig. 14. The matter of dripping the 
risers depends largely on the height of the riser and the judgment of the 
designer. Ordinarily risers less than three stories high are not dripped 
and those more than four stories high are dripped, but there is no set rule 
for this. When risers are dripped the runouts from the steam main may 
be taken from the bottom if desired and each runout then serves as a drip 
for the main. 

The risers are carried up to the highest radiator connection and are 
connected to the radiator through runouts sloping back toward the riser. 
The radiators usually have graduated valves on the supply end, although 
this is not absolutely necessary. Angle-globe valves and gate valves may 
be used where graduated manual control is not desirable. The return 
valves must be of the thermostatic type which will pass air and water but 
which will close against the passage of steam. 

_ The return risers are connected in the basement into a common return 
line, which slopes downward toward the vacuum pump. The vacuum 
pump discharges the air from the system and pumps the water back to the 
boiler, or other receiver, which may be a feed-water tank or a hot well. 
It is essential on these systems that no connection from the supply side 
to the return side be made at any point except through a trap. 

While the best practice demands a return flowing to the vacuum pump 
in an uninterrupted downward slope, in some cases limitations make it 
necessary to drop the return below the level of the vacuum pump inlet 
before the pump can be reached. In such event one of the advantages of 
the vacuum system is that the return can be raised by the suction of the 
vacuum pump to a considerable height, depending on the amount of 
vacuum maintained, by means of a lift fitting inserted in the return. 
Best practice dictates that the lift should be limited to a single lift con- 
nection at the entrance to the vacuum pump and preferably that an 
accumulator tank or receiver with float control be used at the low point 
of the return main at the entrance to the vacuum pump. When the lift 
is considerable, several lift fittings should be used in steps (Fig. 15), 
more successful operation being obtained by this method than when the 
lift is made in one step. If the lift occurs close to the vacuum pump, a 
special arrangement is used as shown in Fig. 16. It is desirable that 
means be provided for draining manually the low point of the lift fittings 
to eliminate from the return piping all water in danger of freezing in case 

285 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 




Supply 



main. 



HartforcU 

return 

connection 




J 



eliminating and pressure 
equalizing device 
See note below* 



^Boilen 



water line 




3==^ ^' ^xWet return 

FIG. 13. TYPICAL ATMOSPHERIC SYSTEM WITH AUTOMATIC RETURN TRAP* 

aProper piping connections are essential with special appliances for pressure equalizing and air eliminatior 



Hartford _| 

return 
connection 




^Uft fitting 
JTrap_ 

Check valve "Bypa'ss'to open drain 

FIG. 14. TYPICAL UP-FEED VACUUM PUMP SYSTEM 



286 



CHAPTER IS. STEAM HEATING SYSTEMS 



the system is shut down for a considerable length of time. Lifts for 
draining condensate from ends of or rises in steam mains should be 
avoided to secure the greatest economy of operation and noiselessness. 

Down-Feed Vacuum System 

The piping arrangement for the down-feed vacuum system is similar 
on the supply side to the down-feed vapor system in that it has similar 
runouts, radiator valves, drips on the bottom of the steam drops, and 
enlargement of the drops for the lower radiator connections. The return 
side of the system is exactly the same as the up-feed system except that 




CU3SE NIPPLE 



9QTEL&CW 



UFTRTnNQ 
MfSCUUM QETUQN 



(JFTFirnMG 



--VACUUM QETUQN 
/UFT FITTING 



FIG. 15. METHOD OF MAKING LIFTS 

ON VACUUM SYSTEMS WHEN DISTANCE 

is OVER 5 FT 




FIG. 16. DETAIL OF MAIN RETURN 
LIFT AT VACUUM PUMP 




BEOUCING 



FIG. 17. METHOD OF CHANGING SIZE OF STEAM MAIN WHEN RUNOUTS 
ARE TAKEN FROM TOP 

the steam riser drips at the bottom are connected into the return line 
through thermostatic traps. It is preferable to take the runouts for the 
risers from the bottom or at a 45-deg angle down from the steam main 
(Fig. 6) so that they may serve as steam main drips. When this is done 
it is practical to run the steam main level if a runout is located at every 
change in pipe size, or if eccentric fittings are used (Fig. 17). A slight 
pitch in the steam main, however, should be used when possible. An 
overhead vacuum down-feed system is shown diagrammatically in Fig. 18. 



SUB-ATMOSPHERIC SYSTEMS 

Sub-atmospheric systems are similar to vacuum systems, but in con- 
trast provide temperature control by variation of the heat output from 
the radiators both by varying the pressure at which steam is circulated in 
the radiation and the amount of steam. The steam supply is continuous 
at varying rates. A vacuum pump capable of operating at high partial 

287 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

vacua is preferable since the higher the vacuum the greater is the accuracy 
in the distribution of steam through the system, particularly in mild 
weather. A pump capable of producing up to 25 in. of vacuum on the 
system is used in such cases. A controller is placed on the pump so that 
the vacuum or absolute pressure carried in the returns can be maintained 
at a certain amount below that existing in the line to insure circulation. 

The traps are designed to operate in high vacuum. It is apparent that 
this system differs from the ordinary vacuum system by haying a vacuum 
on both sides of the system, instead of only on the return side, in order to 
secure control of the heat emission from the radiators and thus to control 



Trap 



Pitch 




Drip trap 



Trap 



^Floor 




4 



* 



Hartford 

return 

connection 




icuum pump, 
FIG. 18. TYPICAL DOWN-FEED VACUUM SYSTEM 



the temperature in the building. These systems permit the heat output 
from the steam mains and risers to be diminished as the weather becomes 
milder, thus giving control to this portion of a heating system. The 
decrease in condensation in the piping as the temperature of the stearn 
is reduced under a vacuum is a measure of the saving in heat loss from 
piping resulting from steam circulation at sub-atmospheric pressures as 
compared with circulation at sub-atmospheric pressure. The system ca.n be 
operated in the same manner as the ordinary vacuum system when desired. 

In the vacuum system, steam pressure above that of the atmosphere 
exists in the supply mains and radiators practically at all times. In the 
sub-atmospheric system, steam pressure exists in the steam main and 
radiators only during the most severe weather, while under average 
winter temperatures the steam is under a partial vacuum which in mild 



CHAPTER 15. STEAM HEATING SYSTEMS 



weather may reach as high as 25 in. after which further reduction in heat 
output is obtained by partially filling the radiation with steam. 

This vacuum is partially self-induced by the condensation of the steam 
in the system due to the supply of steam being furnished through the 
control which admits it, and it being proportioned to balance the existing 
heat loss. To convert an ordinary vacuum return line system to a sub- 
atmospheric system, a control valve is inserted on the steam main near 
the boiler or the boiler is automatically controlled. The steam supply to 
each radiator is provided with a flow proportioning device, such as an 
orifice, a high-vacuum pump is substituted for the ordinary type and is 
supplied with a pressure-difference control, and traps are placed on the 
radiators and drips which will operate satisfactorily at any pressure from 
5 Ib gage to 26 in. of vacuum. 

The control valve is either a special pressure-reducing valve which may 
be controlled manually, or a control valve or combustion equipment 
which may be operated thermostatically from points selected in the 
building. The vacuum pump regulator is simply a diaphragm so ar- 
ranged that, when the vacuum in the return line is insufficient to hold the 
desired difference in pressure between the steam and return sides of the 
system, the vacuum pump is automatically started and the vacuum 
increased to the necessary amount. The actual pressure difference main- 
tained between the two sides of the system is only enough to secure 
adequate circulation and is often about 2 in. of mercury. This fixed 
pressure difference between the supply and return sides of the system 
results in practically constant circulation under all pressure conditions. 

In order to distribute the steam equally w r hen the system is being 
warmed up and also to reduce the amount of steam delivered to the 
radiators on mild days, orifice plates are used in the graduated radiator 
control valves. A definite, nearly constant, relation exists between the 
supply and return pressure differential at various points throughout the 
system which promotes proportionate steam distribution between the 
various radiators. The heat emitted from the radiators in mild weather 
and under conditions of high vacuum is not only reduced in proportion 
to the difference in the steam temperature between that for 2 Ib gage and 
for 25 in. of vacuum but it is reduced still further by a reduction in the 
amount of steam which can pass through the orifice when the steam is 
expanded due to the vacuum. This renders possible the control of heat 
emission from the radiators to a point not indicated entirely by the 
difference in steam temperatures, but far beyond it. 

Sub-atmospheric operation has advantages even where individual 
thermostatic radiator control is installed. By operating the system with 
steam temperatures in parallel with the outside temperature require- 
ments, a large part of the load is removed from the temperature control 
system, it makes fewer operations and the radiator follows an even tem- 
perature without fluctuating from extreme hot to extreme cold. 

The high-vacuum pumps on this system are equipped with receivers 
having float control so that the pump can be placed on a receiver-return- 
pump basis at night if desired so no high vacuum will be carried. One 
radical difference between this system and the ordinary vacuum system 
is that no Hits can be made in the return line, except at the vacuum pump. 

289 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

The returns must grade downward constantly and uninterruptedly from 
the radiator return outlet to the inlet on the high-vacuum pump receiver. 
No attempt should be made to heat service water on this system unless 
the steam line for water heating is taken off the boiler header back of the 
heating system control valve, and then only when 2 Ib or more will be 
carried on the boiler at all times. Sub-atmospheric systems are pro- 
prietary. 

ORIFICE SYSTEM 

Orifice systems of steam heating may have piping arrangements 
identical with vacuum systems but some of these systems omit both the 
radiator thermostatic traps and the vacuum pump in cases where the 
returns are wasted to a sewer or delivered to some type of receiver in 
which no back pressure exists. The principle on which they operate is 
embodied in the well-known fact that an orifice will deliver varying 
velocities when the ratio of the absolute pressures on the two sides of the 
orifice exceeds 58 per cent. If the absolute pressure on the outlet side is 
less than 58 per cent of the absolute pressure on the inlet side no further 
increase in velocity will be obtained. 

As a result, if an orifice is so designed in size as to exactly fill a radiator 
with steam at 2-lb gage on one side and %-lb gage on the other, the abso- 
lute pressure relation is 

14.7 + 0.25 

14.7+2.0 "9 ^ cent 

Should the steam pressure be dropped to %-lb gage, the pressure on each 
side of the orifice would be balanced and no steam flow would take place. 
From this it will be seen that if an orifice of a given diameter will fill a 
given radiator with steam when there is a given pressure on the main, it is 
simply a question of dropping this main pressure provided the supply 
pipe pressures be controlled sufficiently closely, so as to fill any desired 
portion of the radiator down to the point where the main pressure equals 
the back pressure in the radiator, at which time no steam will be supplied 
at all. If orifices throughout a system are designed on a similar basis, all 
radiators will heat proportionately to the steam pressure within the limits 
for which the orifices are designed. 

Some systems use orifices not only in radiator inlets but also at different 
points on the main, thus balancing the system to a greater extent. For 
example, the system may be designed for a particularly long run involving 
an initial pressure of 3-lb gage on the main and 2 Ib at the end of the main, 
but each branch from the main may have an orifice for reducing the 
pressure at it to 2-lb gage. This is particularly useful for branches near 
the boiler where the drop in the main has not yet been produced. 

Orifice systems using a vacuum pump operate successfully with the 
ordinary low vacuum type of pump producing 8 to 10 in. of vacuum. 
They are controlled by various means to regulate the steam pressure. 
One method is by a thermostat located on the roof to govern the steam 
pressure by a combination of outside and inside temperatures; another, 
useful on systems without traps and vacuum pumps, controls the steam 
pressure manually from temperature indication stations in the building, 

200 



CHAPTER 15. STEAM HEATING SYSTEMS 



or automatically by a thermostatically-controlled pressure reduction 
valve or draft regulator on the boiler; with oil or gas firing, the on-and-off 
control or a boiler pressure control may be used. 

ZONE CONTROL 

Certain portions of a building may require more heat at times than 
others but if the whole building is on one general control, such as would 
occur with a single piping system with an on-and-off control or with the 
sub-atmospheric or the orifice systems, it would be necessary to supply 
sufficient heat to accommodate the coldest portion of the building even 
though some sections would be overheated. By separation of a building 
into zones each with its own piping system, each zone of the building may 
be controlled separately. 

The sides of the building with different exposures should be considered 
first, because of ^the varying effects of the wind and sun. With the pre- 
vailing winter winds from the northwest, a simple zoning would place the 
north and west sides of the building on one system and the south and east 
sides on another. If the building is large enough to justify the expendi- 
ture, a better arrangement would be to place all north walls on one zone, 
all west walls on a second, all east walls on a third, and all south walls on 
a fourth. 

In case of high buildings, the lowest 8 or 10 stories may be well protected 
from wind by surrounding buildings, the next 10 stories may have 
moderate exposure, and above this there may be an unobstructed exposure 
to gales. On still days the heat demands vertically will vary little, but on 
windy days there will be a marked difference in the heat requirements for 
the different horizontal sections. In addition, the chimney effect caused 
by the difference in density between the warm air on the inside of a 
building and the colder air on the outside will give an air movement which 
will require zoning to correct. Where such conditions are encountered, 
the building should be divided horizontally as well as vertically. An 
arrangement of this character would give 12 zones: namely, north, east, 
south, and west lower zones; similar middle zones; and similar top zones. 
Each zone should constitute an individual and separate system of piping 
with its own supply steam valve (controlled by thermostats in its respec- 
tive zone) and with its own return or vacuum pump, if one is used. 
Certain interior areas, such as basements, light well walls and other 
locations where sun and wind do not affect the conditions, should be 
placed in still another zone if the most economical results are to be 
secured. 

Zoning has advantages even where individual thermostatic radiator 
control is installed whether this be of pneumatic, electric, or the self- 
contained radiator valve type. By operating each zone to supply heat in 
parallel with its outside temperature and wind fluctuations, a large part 
of the load is taken off the thermostatic controls; they operate less 
frequently and the radiators follow a more even temperature instead of 
fluctuating from extreme hot to extreme cold. 

Sub-atmospheric, orifice, and zone control systems, generally are 
proprietary. Sub-atmospheric systems may be zoned to care for ex- 
posure, occupancy and stack effect. 

291 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



AUXILIARY CONDITIONING UNIT 

In connection with a residential steam or hot water system using 
radiator or convector heating a unit as shown in Fig. 19, is available to 
supplement the old or new system. The unit is arranged in a sheet metal 
enclosure with a filter, circulating fan, means for adding moisture to the 
air, heating or tempering coil and generally provisions are made for the 
addition of a cooling coil in case summer air circulation is desired. The 
unit is frequently located on the ceiling of the basement and is connected 
with one or more supply and return air ducts in the various rooms. In 
some cases, provisions are made for the introduction of a portion of the 
outside air to the system and dampers are included to adjust the desired 
air quantities. 

The heating coil of the unit may be connected to a steam or hot water 
boiler system and is adaptable for operation with a one-pipe, two-pipe or 
vacuum system. The cooling coil may be connected to a source of 

First floor line. 




Canvas connection * 

Sound absorbing 
insulation 



Humidifier 



L7 Vilter 



Motor 



Dampers and 
locking quadrants 



FIG. 19. RESIDENTIAL CONDITIONING UNIT 



refrigeration, or in some cases city water is circulated through the coil 
when 58 F or lower temperature water is available. The amount of 
moisture released is adjustable depending upon the degree of humidifica- 
tion desired. The complete unit may be adapted to various automatic 
control arrangements to satisfy the comfort demands of the occupants. 

CONDENSATION RETURN PUMPS 

Whenever the conditions of a heating system are such that the returns 
from the radiation can not gravitate freely to the boiler, they must be 
returned by some mechanical means such as a condensation pump or a 
return trap. 

The most generally accepted condensation pump unit for low pressure 
heating systems consists of a motor driven centrifugal pump with receiver 
and automatic float control. Other types in use include rotary, screw 
and reciprocating pumps with steam turbine or motor drive, and direct 
acting steam reciprocating pumps. 

Fig. 20 illustrates a typical installation of a motor driven automatic 
condensation unit. It will be noted that the returns flow by gravity to 

292 



CHAPTER 15. STEAM HEATING SYSTEMS 



the vented receiver. As the receiver is filled, the float mechanism operate? 
either a pilot or an across-the-line switch to start the pump, and upon 
emptying the tank disconnects the power and stops it. The pump may 
be used to deliver the condensate direct to the boiler, to a feerhvaier 
heater or to raise the water to any higher elevation or pressure than 
that of the return line. 

A useful application, for instance, is to use a small condensation unit 
to handle a remote section of radiation that otherwise would be difficult 
to grade to the main return. 

The receiver capacities of these automatic units should be sized so as 
not to cause too great a fluctuation of the boiler water line if fed directly 




Trap 



-Air vent 

-Automatic pump and receiver 

x By-pass to drain 
FIG. 20. TYPICAL INSTALLATION USING CONDENSATION PUMP 

to the boiler and at the same time not so small as to cause too frequent 
operation of the unit. The usual unit provides storage capacity between 
stops in the receiver of approximately 1.5 times the amount of condensate 
returned per minute and the pump generally has a delivery rate of 3 to 4 
times the normal flow. 

VACUUM HEATING PUMPS 

On vacuum or sub-atmospheric systems where the returns are under a 
vacuum, it is necessary to use a vacuum pump to discharge the air and 
non-condensable gases to atmosphere and to return the condensate to 
the boiler. Direct acting steam driven reciprocating vacuum pumps are 
sometimes used where high pressure steam is available or where the 
exhaust steam from the pump can be utilized, but in general these have 
been replaced by the automatic motor driven return line vacuum heating 

293 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

pump especially developed for this service. The usual unit consists of a 
compact assembly of air and water removal units driven by one motor 
and furnished complete with receiver, separating tank and full auto- 
matic controls mounted as an integrated unit on one base. 

Practically all of such return line vacuum heating pumps make use of 
the returned condensate to operate either as a liquid piston or as a jet to 
withdraw the air, and in many cases the condensate, from the return line. 
Such hydraulic evacuating devices may be classified as: 

a. Water ring centrifugal displacement pumps. 

b. Water piston pumps. 

c. Stationary water ejector pumps. 

d. Rotary water ejector pumps. 

The evacuating element is generally combined with a centrifugal 
water impeller for the delivery of the condensate to the boiler or feed- 
water heater. 

The assembled units may be further grouped under two general 
classifications: 

fl. Those which perform the function of air separation under atmospheric pressure. 
b. Those which perform the function of air separation under a partial vacuum. 

Pumps coming under the first classification remove both the air and 
condensate from the returns by means of the hydraulic evacuator and 
deliver both to a separating tank under atmospheric pressure. From 
this tank the air and non-condensible vapors are vented to atmosphere 
while the condensate is removed and delivered to the boiler by means of 
the built-in boiler feed pump impeller. 

In the second classification, the air and condensate are first separated 
under vacuum by means of the receiver which is directly connected to 
the returns. The hydraulic evacuator withdraws only the air and non- 
condensible vapors from the top of the receiver and delivers them to 
atmosphere. The built-in condensate pump impeller removes the con- 
densate from the bottom of the receiver and delivers it direct to the 
boiler or feedwater heater. 

Under special conditions such as returning the condensate to a high 
pressure boiler or the furnishing of large air removal units for high 
vacuum systems, it is customary to supply separate motor driven air 
and water pumps. Steam turbine drive is also frequently used where 
high pressure steam is available. There are also special steam turbine 
driven units which are operated by passing the steam to be used in heating 
the building through the turbine with only a 2 to 3 Ib drop across the 
turbine required for its operation. 

For rating purposes 3 vacuum pumps are classified as low vacuum and 
high vacuum. Low vacuum pumps are those rated for maintaining 5J^ in. 
mercury vacuum on the system, and high vacuum pumps are those rated 
to maintain vacuums above SJ^ in. 

The vacuum that may be maintained on a system depends upon the 



'A.S.H.V.E. Standard Code for Testing and Rating Return Line Low Vacuum Heating Pumps, (A.S. 
H.V.E. TRANSACTIONS, Vol. 40, 1934, p. 33). 

294 



CHAPTER 15. STEAM HEATING SYSTEMS 



relationship of the operating air capacity of the hydraulic evacuator at 
the vacuum and temperature of the returns to the air leakage rate into 
the system. It is particularly essential on high vacuum installations 
that the system be tight and that steam be prevented from entering the 
return lines through leaky traps, high pressure drips, etc. 

Vacuum Pump Controls 

In the ordinary vacuum system the vacuum pump is controlled by a 
vacuum regulator which cuts in when the vacuum drops to the lowest 
point desired and which cuts out when the vacuum has been increased 
to the highest point. This is done largely to eliminate the constant 
starting and stopping of the vacuum pump which would occur if the 
vacuum were maintained constant. In addition to this control, a float 
control is included which will automatically start the pump whenever 
sufficient condensation accumulates in the receiver, regardless of the 
vacuum in the system. A selector switch is usually provided to allow 
operation at night as a condensation pump only, also to give continuous 
operation if desired. 

There are several variations to the above control, especially as concerns 
the control of the vacuum maintained on the system. This may be 
accomplished by some form of coordinating control which maintains 
the vacuum of the return system in a pre-determined definite or varying 
relationship to the system supply pressure. 

Piston Displacement Vacuum Pumps 

Piston displacement return vacuum heating pumps may be either 
power or steam driven. They should be provided with mechanical 
lubricators and their piston speed in feet per minute should not exceed 
20 times the square root of the number of inches in their stroke. They 
are usually supplied with an air separating tank, open to atmosphere, 
placed on the discharge side of the pump and at an elevation sufficiently 
high to allow gravity flow of the condensate to the boiler. If the boiler 
pressure is too high for such gravity feed then an additional steam pump 
for feeding the boiler is desirable. The extra pump is sometimes avoided 
by using a closed separating tank with a float controlled vent. In both 
arrangements, the air taken from the system must be discharged against 
the full discharge pressure of the vacuum pump. In the case of high or 
medium pressure boilers, it is better to use the atmospheric separator 
and the second pump. 

In figuring the required displacement for such pumps, a value of from 
6 to 10 times the volumetric flow of condensation is used for average 
vacuums and systems. However, as in the case of return line vacuum 
heating pumps, the displacement is largely dependent upon the tightness 
of the system, the efficiency of the traps and the vacuum that is desired 
to be maintained. 

TRAPS 

Traps are used for draining the condensate from radiators, steam 
piping systems, kitchen equipment, laundry equipment, hospital equip- 
ment, drying equipment and many other kinds of apparatus. The usual 
functions of a trap are to allow the passage of condensate and to prevent the 

295 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

passage of steam. In addition to these functions, traps are frequently 
required to allow the passage of air as well as condensate. Traps are also 
required to allow the passage of air and to prevent the passage of either 
water or steam, or both. 

In addition, traps are used for returning condensate ei thereby gravity, 
by steam pressure, or by both, to a boiler or other point of disposal, and 
for lifting condensate from a lower to a higher elevation, or for handling 
condensate from a lower to a higher pressure. 

The fundamental principle upon which the operation of practically all 
traps depends is that the pressure within the trap at the time of discharge 
shall be equal to, or slightly in excess of, the pressure against which the 
trap must discharge, including the friction head, velocity head and static 
head on the discharge side of the trap. If the static head is in favor of 
the trap discharge it is a minus quantity and may be deducted from the 
other factors of the discharge head. 

Traps may be classified as to function as separating and return or 
lifting traps. Traps may be classified according to the principle of 
operation as (1) float, (2) bucket, (3) thermostatic, (4) tilting, or (5) 
float and thermostatic traps. 

Float Traps. A discharge valve is operated by the rise and fall of a float due to the 
change of water level in the trap. When the trap is empty the float is in its lowest 
position, and the discharge valve is closed. A gage glass indicates the height of water 
in the chamber. 

Unless float traps are well made and proportioned there is danger of considerable 
steam leakage through the discharge valve due to unequal expansion of the valve and 
seat and the sticking of moving parts. The discharge from a float trap is usually con- 
tinuous since the height of the float, and consequently the area of the outlet, is propor- 
tional to the amount of water present. 

Float and thermostatic traps have both a thermostatic element to release air and a 
float element to release the water. 

Bucket Traps. Bucket traps are of two types, the upright and inverted, and although 
they are both of the open float construction, their operating principle is entirely different. 
In the upright bucket trap, the water of condensation enters the trap and fills the space 
between the bucket and the walls of the trap. This causes the bucket to float and forces 
the valve against its seat, the valve and its stem usually being fastened to the bucket. 
When the water rises above the edges of the bucket it flows into it and causes it to sink, 
thereby withdrawing the valve from its seat. This permits the steam pressure acting 
on the surface of the water in the bucket to force the water to a discharge opening. When 
the bucket is emptied it rises and closes the valve and another cycle begins. The discharge 
from this type of trap is intermittent. 

In the inverted bucket trap, steam floats the inverted submerged bucket and closes the 
valve. Water entering the trap fills the bucket which sinks and through compound 
leverage opens the valve, and the trap discharges. It is impossible to install a water 
gage glass on an inverted bucket trap, but if visual inspection is necessary, a gage glass 
can be placed on the line leading to the trap. No air relief cocks can be used, but this is 
unnecessary, as the elimination of air is automatically taken care of by air passing through 
the vent in the top of the inverted bucket regardless of temperature. 

Thermostatic Traps. Thermostatic traps are of two types, those in which the discharge 
valve is operated ^by the relative expansion of metals, and those in which the action of 
a volatile liquid is utilized for this purpose. Thermostatic traps of large capacity for 
draining blast coils or very large radiators are called blast traps. 

Tilting Traps. With this type of trap, water enters a bowl and rises until its weight 
overbalances that of a counter-weight, and the bowl sinks to the bottom. As the bowl 
sinks, a valve is opened thus admitting live steam pressure on the surface of the water 
and the trap then discharges. After the water is discharged, the counter-weight sinks 
and raises the bowl, which in turn closes the valve and the cycle begins again. Tilting 

296 



CHAPTER 15. STEAM HEATING SYSTEMS 



traps are necessarily intermittent in operation. They are not ordinarily equipped with 
glass water gages, as the action of the trap shows when it is filling or emptying. The air 
relief of tilting traps is taken care of by the valves of the trap. 

Thermostatic traps are generally used for draining radiators and 
heaters, except for very large capacities where bucket, float or blast-type 
thermostatic traps are used. Thermostatic traps for this service usually 
pass both condensate and air and in the case of float and upright bucket 
traps the air is usually relieved through an auxiliary thermostatic trap in 
a by-pass around the main trap. Sometimes this auxiliary air trap is an 
integral part of the trap. Such traps are termed float and thermostatic 
traps. 

Blast-type thermostatic traps are sometimes used on vacuum heating 
systems for connecting old one- or two-pipe gravity systems in parallel 
with vacuum return line systems, in which case the blast-type thermo- 
static traps should not be provided with auxiliary air by-pass, as the 



High pressure drip 
valve 



.Vent to heat main 
or atmosphere 




T Connection to main 
vacuum return 



A -* Dirt. 
High pressure trap pocket 



Low pressure trap 



FIG. 21. METHOD OF DISCHARGING HIGH- PRESSURE APPARATUS INTO LOW-PRESSURE 

HEATING MAINS AND VACUUM RETURN MAINS THROUGH 

A LOW-PRESSURE TRAP 

action of this will allow the vacuum to draw air into the old system 
through its "air valves, especially when the steam is wholly or partially 
cut off. The air from the returns of such old systems should be relieved 
just ahead of the traps by means of quick-venting automatic air valves, 
preferably of the non-return type, especially if the other air valves on 
the old system are non-return valves. 

Return traps used for discharging to a higher or a lower pressure are 
provided with two or three valves operated by the action of the trap. 
In the case of the two-valve return traps, one valve closes a steam inlet 
and the other valve opens a vent outlet while the trap is filling, and as 
soon as the trap dumps, the first valve opens the steam inlet and the 
second valve closes the vent outlet, while the trap discharges. In this 
type of trap there must be a swinging check-valve on each side of the 
trap, in addition to the usual by-pass, to prevent the pressure in the trap, 
while discharging, from backing up through the inlet and the pressure 
in the discharge line from backing up into the trap while it is filling. This 

297 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



type of trap will blow steam out through the vent while filling, if the 
pressure on the inlet side is sufficient, and should not be used, therefore, 
with such pressures unless the vent is properly piped back into the return 



Swing check valvex 
Check valv 



Gage glass 



Returns 



/Thermostatic air valve 
- Safety valve to waste 
Check valve 

Connection 

for test 

gage 




Drip valve 
-from 
strainer 



FIG. 22. RETURN TRAP AND RECEIVER FOR AUTOMATIC BOILER FEED 

to a feed water heater, a condenser or a perforated pipe in the bottom 
of the receiver to which the trap discharges in such a way as to prevent 
the escape of the steam that comes in with the condensate and passes 
through the vent. In the three-valve traps of this type there is an extra 

298 



CHAPTER 15. STEAM HEATING SYSTEMS 



valve for closing the discharge while the trap is filling with condensate. 
High pressure traps should not discharge directly into a vacuum return 
because of the vapor formed by the re-evaporation of a part of the hot 
condensation. Fig. 21 shows a method which may be used for disposing of 
the greater part of the vapor of re-evaporation. An expansion chamber 
often is installed between the high- and low-pressure traps. 

Automatic Return Traps 

In the general heating plant, where thermostatic traps are installed on 
the heating units, it becomes necessary to provide a means for returning 
the water of condensation to the boiler, if a condensation or vacuum pump 
is not used. When the return main can be kept sufficiently high above the 
boiler water line for all operating conditions, the water of condensation 
will flow back by gravity, and no mechanical device is required. But 
actually this does not work out in practice. It follows, therefore, that a 
direct return trap is needed for the handling of the condensation even 
though it may not be called into action except under some operating 
condition where the pressure differential exceeds the static head provided. 
The installation of a direct return trap assures safety for such systems, 
and guarantees the operation of the plant under varying conditions. 

Automatic return traps, sometimes called alternating receivers, may 
be of the counter-balanced, tilting type, or spring actuated. These consist 
of a small receiver with an internal float, and when the condensate will 
not flow into the boiler under pressure, it will feed into the receiver of the 
trap, and in so doing, raise or tilt the float or mechanism which actuates a 
steam valve automatically. This admits steam to the receiver, at boiler 
pressure, and the equalizing of the pressures which follows allows the 
water to flow into the boiler. Fig. 22 shows a direct return tilting trap 
and receiver properly connected for automatically feeding a boiler from a 
system of returns delivering the condensate to the receiver. 



PROBLEMS IN PRACTICE 

1 What is meant by water line difference in a gravity steam heating system? 

The water line difference is the distance between the level of the water in the dry or wet 
return and the boiler water line. This difference is equivalent to the pressure required 
to overcome the maximum drop in the system and the operating pressure of the boiler. 

2 How many types of common mechanical returns are there and what are 
they? 

Three: (1) the mechanical return trap, (2) the condensation return pump, and (3) 
the vacuum pump. 

3 In the ordinary vacuum system of steam heating, where does the vacuum 
usually exist? 

On the return side of the system only, between the radiator trap and the vacuum pump. 
If the radiator supply valve is closed off, the vacuum may extend back through the 
radiator as far as the supply valve; if an inadequate supply of steam is furnished to 
the system, some vacuum may be developed in the steam main, but neither of these can 
be termed normal operation. 

299 



HEATING VENTIIATING AIR CONDITIONING GUIDE 1938 

4 What is the distinction between the open and the closed vapor systems? 

The open vapor system has the return line always open to the atmosphere, while the 
closed vapor system has an automatic device on the air vent so that air once expelled 
from the system through the vent cannot re-enter via this route. 

5 On a vacuum system, what device must be placed on all drips before they 
enter the vacuum return line? 

A thermostatic drip trap or occasionally, where large volumes of condensation are to be 
handled, a float trap, or combination float and thermostatic trap. 

6 How does the sub-atmospheric system differ in operation from the ordinary 
vacuum system? 

The ordinary vacuum system has pressure in the steam line, and a vacuum produced by 
the vacuum pump in the return line, usually varying between 5 and 10 in. of mercury. 
The sub-atmospheric system may have either a vacuum or pressure on the steam and 
return lines according to the weather conditions, but a constant difference in pressure is 
maintained between the lines regardless of what vacuum may be carried. The vacuum, 
which is generally produced jointly by condensation and the exhausting action of the 
pump, in the system under conditions of throttled steam supply, will run much higher 
than in the ordinary vacuum system, and as high as 25 in. of mercury in the radiators. 

7 What is generally understood by zoning in building steam heating systems? 

Zoning is a term applied to the placing of certain sections of a building on a single 
temperature control instead of having either individual room control or a single tempera- 
ture control governing the whole building. Zones may be horizontal, such as a single 
story, a basement, or an attic, or vertical such as the north side, or the west side. 

8 Why does the water line in the far end of a wet return in a. gravity steam 
system rise higher than the water line in the boiler? 

The friction of the steam flowing through the steam main from the boiler to the far end of 
the system and the pressure reduction resulting from the condensing action of the radi- 
ators causes a drop in steam pressure at the point where the wet return is connected; 
consequently, the steam pressure on top of the water in the wet return is less than the 
steam pressure on top of the water in the boiler, so the water in the end of the wet return 
rises until a balanced condition is set up. 

9 On gravity one-pipe systems as indicated hi Fig. 1 and Fig. 3, why is the 
drip on the steam runout connected to wet return? 

Because if it were connected to dry return, the pressure drops to two different points 
would not necessarily be the same and the system would short circuit. 

10 What is the function of the automatic return trap? 

To insure the return of condensate to the boiler when the operating condition is such that 
the boiler pressure exceeds the static head on the returns. 

11 "What advantage is there to an air valve with a check to prevent the re- 
entrance of expelled air? 

A system equipped with such valves builds up a vacuum and holds the heat longer. 
With proper controls on the boiler, lower radiator temperatures can be maintained in 
mild weather, giving better plant efficiency. 

12 What are the essentials of a two-pipe closed vapor system? 

Packless graduated valves on radiators; thermostatic return traps on return and drips; 
an automatic return trap to prevent water from backing out of the boiler. 

13 Why must the automatic return trap on two-pipe vapor systems be about 
18 in. above the boiler water line? 

That height is necessary to overcome water line difference owing to pressure drop and 
friction in pipe and fittings. 

300 



Chapter 16 

PIPING FOR STEAM HEATING SYSTEMS 

Flow of Steam in Pipes, Pipe Sizes, Tables for Pipe Sizing, 
One-Pipe Gravity Air Vent Systems, Two-Pipe Gravity Air 
Vent Systems, Two-Pipe Vapor Systems, Vacuum Systems, 
Atmospheric Systems, Sub-Atmospheric Systems, Orifice 
Systems, High Pressure Steam, Expansion in Steam and 
Return Lines, Piping Connections and Details, Boiler Con- 
nections, Hartford Return Connection 

THE design of a steam heating system should be considered under four 
headings, namely, (1) the details of the heating units, (2) the arrange- 
ment of the general piping scheme, (3) the details of connections, and (4) 
the sizing of the lines. Items 1 and 2 are covered in Chapters 14 and 15, 
respectively, while this chapter considers the two latter items. 

The functions of piping are to supply the heating units with steam and 
to remove the condensation. In some systems both the air and con- 
densation are removed from the heating units by the return piping. To 
accomplish this effectively, the distribution of the steam should be 
efficient and equitable, without noise, and the returns should be as short 
as possible. When air is handled its escape should be facilitated to the 
utmost since an air-bound system will not heat properly. Condensation 
takes place in a steam system not only in the heating units, but through- 
out the piping system as well, and the returns also condense any steam or 
vapor that may be contained. At the same time part of the condensation 
may flash back into steam when the vacuum or pressure in the return is 
considerably below the steam pressure. 

It is essential that steam piping systems not only distribute steam at 
full load but also at partial loads, as the average winter demand is less 
than half of the demand in most severe outside temperatures. Further- 
more, in heating up rapidly the load on the steam main may exceed the 
maximum operating load even in extreme weather, due to the necessity 
of raising the temperature of the metal in the system to the steam tem- 
perature. This may require more heat than would be emitted from the 
system itself after it once is thoroughly heated. 

STEAM FLOW 

The rate of flow of dry steam or steam with a small amount of water 
flowing in the same direction is in accordance with the general laws of gas 
flow and is a function of the length and diameter of the pipe, the density 
of the steam, and the pressure drop through the pipe. This relationship 
of flow of dry steam or steam with a small amount of water has been 

301 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

established by Babcock in formula 1. 

P = 0.0000000367 ( H" ^) jff- (1) 

or 



w-saao+l, M\ L <2) 



where 

P loss in pressure, pounds per square inch. 

d = inside diameter of pipe, inches. 

L = length of pipe, feet. 

D = weight of 1 cu ft of steam. 

W = weight of steam flowing per hour, pounds. 

Example 1. How much steam will flow per hour through JLOO ft of 2-in. pipe if the 
initial pressure is 1.3 Ib per square inch and the pressure drop is 1 oz? 

Solution. P - ^ - 0.0625 Ib; d = 2.067 in. (Table 1, Chapter 18); L - 100 ft; 
D - 0.04038 Ib (Table 8, Chapter 1). Substituting these values in Formula 2: 

V 0.0625 X 0.04038 X 2.067* 
7 3.6 \ = 97.2 Ib per hour. 



. 
7 3.6 \ 

\ 1 + 2356T/ 



Formula 2 does not allow for entrained water in low-pressure steam, 
condensation in pipe, and roughness in commercial pipe as found in 
practice. 

The latent heat of steam (&f g ) at atmospheric pressure (Table 8, 
Chapter 1) is 970.2 Btu per pound. Inasmuch as the heat emission of an 
equivalent square foot of heating surface (radiation) is 240 Btu, 1 Ib of 

970 2 

steam at this pressure will supply ' or 4.04 sq ft of equivalent heating 



surface. This figure is usually taken as 4 even. In Example 1, the weight 
of steam flowing per hour would therefore supply 4 X 97.2 or 388.8 sq ft 
of equivalent heating surface. 

PIPE SIZES 

The determination of pipe sizes for steam heating depends on the 
following principal factors: 

1. The initial pressure and the total pressure drop which may be allowed between the 
source of supply and the end of the return system. 

2. The maximum velocity of steam allowable for quiet and dependable operation of 
the system. 

3. The equivalent length of the run from the boiler or source of steam supply to the 
farthest heating unit. 

4. Unusual conditions in the building to be heated. 

Initial Pressure and Pressure Drop 

Theoretically there are several factors to be considered, such as initial 
pressure and pressure required at the end of the line, but it is most im- 
portant that (1) the total pressure drop does not exceed the initial pressure 
of the system; (2) the pressure drop is not so great as to cause excessive 
velocities; (3) there is a constant initial pressure, except on systems 
specially designed for varying initial pressures, such as tfie sub-atmos- 

302 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 

pheric which normally operate under controlled partial vacua, the orifice, 
and the vapor systems which at times operate under such partial vacua 
as may be obtained due to the condition of the fire; (4) there is sufficient 
difference in level, for gravity return systems, between the lowest point 
on the steam main, the heating units, and the dry return, when considered 
in relation to the boiler water line. 

All systems should be designed for a low initial pressure and a reason- 
ably small pressure drop for two reasons: first, the present tendency in 
steam heating unmistakably points toward a constant lowering of pres- 
sures even to those below atmospheric; second, a system designed in this 
manner will operate under higher pressures without difficulty. When a 
system designed for a relatively high initial pressure and a relatively high 
pressure drop is operated at a lower pressure, it is likely to be noisy and 
have poor circulation. 

The total pressure drop should never exceed one-half of the initial 
pressure when condensate is flowing in the same direction as the steam. 
Where the condensate must flow counter to the steam, the governing 
factor is the velocity permissible without interfering with the condensate 
flow. Laboratory experiments limit this to the capacities given in 
Tables 1 and 2 for vertical risers and in Table 3 for horizontal pipes at 
varying grades. 

Maximum Velocity and Reaming 

The capacity of a steam pipe in any part of a steam system depends 
upon the quantity of condensation present, the direction in which the 
condensate is flowing, and the pressure drop in the pipe. Where the 
quantity of condensate is limited and is flowing in the same direction as 
the steam, only the pressure drop need be considered. When the con- 
densate must flow against the steam, even in limited quantity, the ve- 
locity of the steam must not exceed limits above which the disturbance 
between the steam and the counter-flowing water may produce object- 
ionable sounds, such as water hammer, or may result in the retention of 
water in certain parts of the system until the steam flow is reduced 
sufficiently to permit the water to pass. The velocity at which such 
disturbances take place is a function of (1) the pipe size, whether the pipe 
runs horizontally or vertically, (2) the pitch of the pipe if it runs hori- 
zontally, (3) the quantity of condensate flowing against the steam, and 
(4) freedom of the piping from water pockets which under certain con- 
ditions act as a restriction in pipe size. 

Three factors of uncertainty always exist in determining the capacity 
of any steam pipe. The first is variation in manufacture, which appar- 
ently cannot be avoided and which caused an actual difference of 20 per 
cent in the capacity of a 1-in. pipe in experiments carried on at the 
A.S.H.V.E. Research Laboratory (Table 4). The second is the reaming 
of the ends of the pipe after cutting, which, experiments indicate, might 
reduce the capacity of a 1-in. pipe as much as 28.7 per cent (Table 5). 
The third is the uniformity in grading the pipe line. All of the capacity 
tables given in this chapter include a factor of safety. However, the pipe 
on which Table 4 is based showed no particular defects or constrictions 
on the inside, and the factor of safety referred to does not cover abnormal 
defects or constrictions nor does it cover pipe not properly reamed. 

303 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 1. MAXIMUM ALLOWABLE CAPACITIES OF UP-FEED RISERS FOR ONE-PIPE 

Low PRESSURE STEAM 

Based on A. S. H. V. E. Research Laboratory Tests 



POTS SIZE 
INCHES 


VELOCITT 
FEET PER SECOND 


PRESSURE DROP 
OUNCES 

PEE 100 FT 


CAPACITY 


SqFt 
Radiation 


Btu per Hour 


Lb 
Steam per Hour 


A 


B 


C 


D 


E 


F 


1 


14.1 


0.68 


45 


10,961 


11.3 


1J 


17.6 


0.66 


98 


23,765 


24.5 


1J* 


20.0 


0.66 


152 


36,860 


38.0 


2 


23.0 


0.57 


288 


69,840 


72.0 


m 


26.0 


0.54 


464 


112,520 


116.0 


3 


29.0 


0.48 


799 


193,600 


199.8 


3J 


31.0 


0.44 


1144 


277,000 


286.0 


4 


32.0 


0.39 


1520 


368,000 


380.0 



INSTRUCTIONS FOR USING TABLE 1 

1. Capacities given in Table 1 should never be exceeded on one-pipe risers. 

2. Capacities are based on J^-lb condensation per square foot eQuivalent radiation and actual diameter 
of standard pipe. 

3. All pipe should be well reamed and free from constrictions. Fittings should be up to size. (See 
Tables 4 and 5). 



TABLE 2. MAXIMUM ALLOWABLE CAPACITIES OF UP-FEED RISERS FOR TWO-PIPE 
Low PRESSURE STEAM 

Based on A. S. H. V. E. Research Laboratory Tests 



PIPE SIZE 
INCHES 


VELOCITY 
FEET PER SECOND 


PRESSURE DROP 
OUNCES 
PER 100 FT 


CAPACITT 


SqFt 
Radiation 


Btu per Hour 


Lb 
Steam per Hour 


A 


B 


C 


D 


E 


F 


H 


20 





40 


9550 


10.0 


1 


23 


1.78 


74 


17,900 


18.45 


1 


27 


1.57 


151 


36,500 


37.65 


1H 


30 


1.48 


228 


55,200 


57.0 


2 


35 


1.33 


438 


106,100 


109.5 


m 


38 


1.16 


678 


164,100 


169.4 


3 


41 


0.95 


1129 


273,500 


282.2 


3H 


42 


0.81 


1548 


375,500 


387.0 


4 


43 


0.71 


2042 


495,000 


510.5 



INSTRUCTIONS FOR USING TABLE 2 

1. The capacities given in this table should never be exceeded on two-pipe risers. 

2. Capacities are based on K-lb condensation per square foot equivalent radiation and actual diameter 



of standard pipe. 

3. All pipe should be well reamed and free from constrictions. Fittings should be up to i 
Tables 4 and 5.) 

304 



(See 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 



TABLE 3. COMPARATIVE CAPACITY OF STEAM LINES AT VARIOFS PITCHES FOR STEAM 

AND CONDENSATE FLOWING IN OPPOSITE DlRECTIONS a 

Pitch of Pipe in Inches per 10 Ft 



PITCH OF 








, 






















PIPE 


2* i 


N. 


H i 


N. ] ID 


r. 


1'ai 




2 




3D 




4 IN. 


Si? 


r. 


Pipe 

fcize 
In'hes 


SiFt 
Had. 
Baaed 
on 240 
Bta 


Max.Vel. 


Si Ft 
Rad. 
Based 
on 240 
Btu 


_ i Sq Ft 

5 Rad. 
W iBawid 

J3 on 240 

* j Btu 




SqFt 

Based 
on 240 
Btu 


Max.Vel. 


SqFt 
Rad. 
Based 
on 240 
Btu 


m 

I 


SqFt 
Rad. 
Baaed 
on 240 
Btu 


Max.Vri. 


&2|* 

Bae*-i C' 

on 240 45 
Btu ; * 


SqFt 
Rad. 
Based 
on 240 
Btu 


MM.VeL 


S x 


25. 


12 


30.3 


14 I 37.3 




40.4 


19 


42.5 


20 


46.1 


21 


47.5 { 22 


49.3 


7,3 


1 


45.8 


12 


52.6 


15 63.0 


17 


70.0 


20 


75.2 


2? 


83.0 




87.9 J 25 


90.2 




1^ 


104.9 


IS 


117.2 


20 1 133. 


23 


144.5 


25 


154.0 


27 


165.0 


2ft 


172.6 < 29 


178.2 


31 


Jl^ 


142.6 


18 


159.0 


21 i 181.0 


23 


196.5 


25 


209.3 


27 


224.0 


28 


234.8 , 50 


242.6 


3t 


2 


236.0 


19 


263.5 


20 J 299.5 


23 


325.5 


25 


346.5 


27 


371.5 


28 


3SS.4 j 29 

; 


401.1 


30 



Data from AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS Research Laboratory. 

Equivalent Length of Run 

All tables for the flow of steam in pipes, based on pressure drop, must 
allow for the friction offered by the pipe as well as for the additional 
resistance of the fittings and valves. These resistances generally are 
stated in terms^of straight pipe; in other words, a certain fitting will 
produce a drop in pressure equivalent to so many feet of straight run of 
the same size of pipe. Table 6 gives the number of feet of straight pipe 
usually allowed for the more common types of fittings and valves. In all 
pipe sizing tables in this chapter the length of run refers to the equivalent 
length of run as distinguished from the actual length of pipe in feet. The 
length of run is^not usually known at the outset; hence it is necessary to 
assume some pipe size at the start. Such an assumption frequently is 
considerably in error and a more common and practical method is to 
assume the length of run and to check this assumption after the pipes are 
sized. For this purpose the length of run usually is taken as double the 
actual length of pipe. 

TABLE 4. PER CENT DIFFERENCE IN CAPACITY FOR CARRYING STEAM AND CONDENSATE 
DUE TO VARIATION OF PIPE SIZE AND SMOOTHNEss a 





MAXIMUM CONDENSATION, LB PER HOUR 


Size of pipe 


XIn. 


lln. 


IX In. 


lIn. 


Minimum.- 


14.00 
15.20 


24.89 
30.08 


45.42 
52.08 


70.50 
82.00 


Maximum 
Per cent variation 


8.6 


20.8 


14.7 


16.3 



aData from AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS Research Laboratory. 
TABLE 5. EFFECT OF REAMING ENTRANCE TO ONE-INCH ONE-PIPE RISERS* 





MixnniM CAPACITY 
ov RISER 


PEE CENT 
DECREASE 


Reamed entrances 


24.7 Ib per hour 
23.9 Ib per hour 
22.2 Ib per hour 
19.2 Ib per hour 
17.6 Ib per hour 


0.0 
3.2 
10.1 
22.2 

28.7 


Rounded entrances. 


Squared entrances 
Three wheel cutter. . 


Single wheel cutter. 



Data from AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS Research Laboratory. 

305 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 6. LENGTH IN FEET OF PIPE TO BE ADDED TO ACTUAL LENGTH OF RUN 
OWING TO FITTINGS TO OBTAIN EQUIVALENT LENGTH 



SIZE OF PIPE 
INCHES 


ST'D. ELBOW 


SIDE OUTLET 
TEE 


GATE VALVE 


GLOBE VALVE 


ANGLE VALVE 


Length in Feet to be Added to Run 


2 


5 


16 


2 


18 


9 


2H 


7 


20 


3 


25 


12 


3 


10 


26 


3 


33 


16 


3Ji 


12 


31 


4 


39 


19 


4 


14 


35 


5 


45 


22 


5 


18 


44 


7 


57 


28 


6 


22 


50 


9 


70 


32 


7 


26 


55 


10 


82 


37 


8 


31 


63 


12 


94 


42 


9 


35 


69 


13 


105 


47 


10 


39 


76 


15 


118 


52 


12 


47 


90 


18 


140 


63 


14 


53 


105 


20 


160 


72 



Example of length in 
feet of pipe to be added 
to actual length of run. 




TABLES FOR PIPE SIZING 1 

Factors determining the size of a steam pipe and its allowable limit of 
capacity are as follows: 

1. Pipe condensate flowing with steam. 

2. Pipe condensate flowing against steam. 

3. Pipe and radiator condensate flowing with steam. 

4. Pipe and radiator condensate flowing against steam. 

It is apparent that (3) and (4) are practically limited to one-pipe 
systems while (1) and (2) cover all other systems. 

Tables 7 and 8, worked out for determining pipe sizes, have their col- 
umns lettered continuously, Columns A through L being in Table 7, and 
M through EE in Table 8. In the following text, reference made to 
columns will be by letter. The tables are based on the actual inside 
diameters of the pipe and the condensation of J^ lb (4 oz) of steam per 
square foot of equivalent direct radiation 2 (abbreviated EDR) per hour. 
The drops indicated are drops in pressure per 100 ft of equivalent length 
of run. The pipe is assumed to be well reamed without unusual or notice- 
able defects. 



J Pipe size tables in this chapter have been compiled in simplified and condensed form for the convenience 
of the user; at the same time all of the information contained in previous editions of THE GUIDE has been 
retained. Values of pressure drops, formerly expressed in ounces, are now expressed in fractions of a pound. 

*As steam system design has materially changed in recent years so that 240 Btu no longer expresses the 
heat of condensation, from a square foot of radiator surface per hour, and as present day heating units have 
different characteristics from older forms of radiation, it is the purpose of THE GUIDE to gradually eliminate 
the empirical expression square foot of equivalent direct radiation. EDR, and to substitute a logical unit based 
on the Btu. The new terms to express the equivalent of 1000 Btu (Mb), and 1000 Btu per hour (Mbh), 
have been approved by the A.S.H.V.E. 

306 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 



Table 7 may be used for sizing piping for steam heating systems by 
determining the allowable or desired pressure drop per 100 equivalent 
feet of run and reading from the column for that particular pressure drop. 
This applies to all steam mains on both one-pipe and two-pipe systems, 
vapor systems, and vacuum systems. Columns B to G, inclusive, are used 
where the steam and condensation flow in the same direction, while 
Columns H and I are for cases where the steam and condensation flow in 
opposite directions, as in risers and runouts that are not dripped. Columns 
/, K t and L are for one-pipe systems and cover riser, radiator valve, and 
vertical connection sizes, and radiator and runout sizes, all of which are 
based on the critical velocities of the steam to permit the counter flow of 
condensation without noise. 

Sizing of return piping may be done with the aid of Table 8 where pipe 
capacities for wet, dry, and vacuum return lines are shown for the pressure 
drops per 100 ft corresponding to the drops in Table 7. It is customary to 
use the same pressure drop on both the steam and return sides of a system. 

TABLE 7. STEAM PIPE CAPACITIES 

Capacity Expressed in Square Feet of Equivalent Direct Radiation 
(Reference to this table will be by column letter A through L) 

This table is based on pipe size data developed through the research investiga- 
tions of the AMERICAN SOCIETY OF HEATING AND VENTILATING ENGINEERS. 



CAPACITIES OF STEAM MAINS AND RISERS 


SPECIAL CAPACITIES F-OR 




OmB-PiFR SYSTEMS ONLT 




DIRECTION or CONDENSATION FLOW IN Pxra Lunc 




PIPE 
SIZE 
Iv 


With the Steam in One-Pipe and Two-Pipe Systems 


Against the Steam 
Two-Pipe Only 


Supply 
Risers 


Radiator 
Valves 
and 


Radiator 
and 
Riser 


Vsa Ib 


1/2* Ib 


Vie Ib 


Hlb 


Klb 


J*lb 




or 


or 


or 


or 


or 


or 




Up- 


Vertical 






MOz 
Drop 


MOz 
Drop 


lOz 
Drop 


20z 
Drop 


40z 
Drop 


80z 
Drop 


Vertical 


Hori- 
zontal 


Fe5 


Con- 
nections 


Run- 
outs 


A 


B 


C 


Z> 


E 


F 





ff 


/c 


/b 


K 


L 


% 






30 








30 




25 








39 


46 


56 


79 


iff 


157 


56 


26 


45 


20 


20 


IK 


87 


100 


122 


173 


245 


346 


122 


58 


98 


55 


55 


IK 


134 


155 


190 


269 


380 


538 


190 


95 


152 


81 


81 


2 


273 


315 


386 


546 


771 


1,091 


386 


195 


288 


165 


165 


2^ 


449 


518 


635 


898 


1,270 


1,797 


635 


395 


464 




260 




822 


948 


1,163 


1,645 


2,326 


3,289 


1,129 


700 


799 




475 


m 


1,228 


1,419 


1,737 


2,457 


3,474 


4,913 


1,548 


1,150 


1,144 




745 


4 


1,738 


2,011 


2,457 


3,475 


4,914 


6,950 


2,042 


1,700 


1,520 





1,110 


5 


3,214 


3,712 


4,546 


6,429 


9,092 


12,858 




3,150 






2,180 


6 


5,276 


6,094 


7,462 


10,553 


14,924 


21,105 


......... 


........ 











8 


10,983 


12,682 


15,533 


21,967 


31,066 


43,934 


........ 


.._. 


........ 


___ 





10 


20,043 


23,144 


28,345 


40,085 


56,689 


80,171 














12 


32,168 


37,145 


45,492 


64,336 


90,985 


128,672 





_ 









16 


60,506 


69,671 


84,849 


121,012 


169,698 


242,024 



















An Horizontal Mains and Down-Feed Risers 


Up- 

Fned 


Mains 
andTJn- 
dripped 


Up- 
Feed 


Radiator 
Con- 


Run- 
outs 
Not 






Risers 


Run- 
outs 


Risers 


nections 


Dripped 



Note. All drops shown are in pounds per 100 ft of equivalent run baaed on pipe properly reamed. 
aDo not use Column H for drops of 1/24 or 1/32 Ib; substitute Column C or Column B as required. 
bDo not use Column J for drop of 1/32 Ib except on sizes 3 in. and over; below 3 in. substitute Column B. 
On radiator runouts over 8 ft long increase one pipe size over that shown in Table 7. 

f AMERICAN SOCIETY OF HEATING AND VENTILATING EWGIVEBRS \ Not to be Reprinted With- 
| HeaKngt p iping an & ^ Conditioning Contraeton Naiiond Aaociatim j out Special Permission 

307 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



a a 

I 



gis: 

ftg; 

e.m 



W *^ ** Oj 

^3 B 

"111 

III 



i! 



T-t ON f*5 CO f*5 C 



II! 



!i 



i-tCM CO<*J>-CM 






: *H csi PO oo PO - 



SVO O O O O f 
O^OO 1 * t^^-i 
Nt*vOvO*O^ it^-c 

MOC<J^H^OO 

1-1 c<i ro to oo 



IBl 



^H*HTt<VOOVOCNOO 



OVOCNOOCM 

1-1 1-1 CM CO VQ 



rv i > 4T-. *^- t-> tJ i j 

^rjTvoo*vcTcM" S i 

i I i-l CM 



cot-c 

^-1 rH CO IQ 









? OC 

Pcsc 






308 



*" o\ $* o cs to o oo c5 o 



3li M ! j ; 

^Tco* i i : : i 



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i-l CS CO IQ OQ 



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;;;;;;;;: 



i i i i ! > 
! i i I ! 



S. 



r-K 



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1 

3 

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1 

I 



I! 

Kft, 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 



Example 2. What pressure drop should be used for the steam piping of a system if 
the measured length of the longest run is 300 ft and the initial pressure is not to be over 
2-lb gage? 

Solution. It will be assumed, if the measured lengtn of the longest run is 500 ft, that 
when the allowance for fittings is added the equivalent length of run will not exceed 
1,000 ft. Then, with the pressure drop not over one half of the initial pressure, the drop 
could be 1 Ib or less. With a pressure drop of 1 Ib and a length of run of 1,000 ft, the 
drop per 100 ft would be Ho ft), while if the total drop were J^ Ib, the drop per 100 ft 
would be }>20 lb- * n *!} e ^ rst instance the pipe could be sized according to Column D for 
?^6 Ib per 100 ft, and in the second case, the pipe could be sized according to Column C 
for } 34 Ib. On completion of the sizing, the drop could be checked by taking the longest 
line and actually calculating the equivalent length of run from the pipe sizes determined. 
If the calculated drop is less than that assumed, the pipe size is all right; if it is more, it is 
probable that there are an unusual number of fittings involved, and either the lines must 
be straightened or the column for the next lower drop must be used and the lines resized. 
Ordinarily resizing will be unnecessary. 

ON&PIPE GRAVITY AIR-VENT SYSTEMS 

One-pipe gravity air-vent systems in which the equivalent length of run 
does not exceed 200 ft should be sized as follows: 

1. For the steam main and dripped runouts to risers where the steam and condensate 
flow in the same direction, use Ke-lb drop (Column D). 

2. Where the riser runouts are not dripped and the steam and condensation flow in 
opposite directions, and also in the radiator runouts where the same condition occurs, use 
Column L. 

3. For up-feed steam risers carrying condensation back from the radiators, use Column 7, 

4. For down-feed systems the main risers of which do not carry any radiator con- 
densation, use Column H. 

5. For the radiator valve size and the stub connection, use Column K. 

6. For the dry return main, use Column U. 

7. For the wet return main use Column T. 

On systems exceeding an equivalent length of 200 ft, it is suggested that 
the total drop be not over % Ib. The return piping sizes should correspond 
with the drop used on the steam side of the system. Thus, where M-t-lb 
drop is being used, the steam main and dripped runouts would be sized from 
Column C; radiator runouts and undripped riser runouts from Column L; 
up-feed risers from Column J; the main riser on a down-feed system from 
Column C (it will be noted that if Column H is used the drop would 
exceed the limit of }^4 Ib) ; the dry return from Column R; and the wet 
return from Column Q. 

With a 3^2-lb drop the sizing would be the same as for J^4 Ib except that 
the steam main and dripped runouts would be sized from Column 5, the 
main riser on a down-feed system from Column J5, the dry return from 
Column 0, and the wet return from Column N. 

Example 3. Size the one-pipe gravity steam system shown in Fig. 1 assuming that 
this is all there is to the system or that the riser and run shown involve the longest run 
on the system. 

Solution. The total length of run actually shown is 215 ft. If the equivalent length 
of run is taken at double this, it will amount to 430 ft, and with a total drop of }4 Ib 
the drop per 100 ft will be slightly less than He Ib. It would be well in this case to use 
H* lb t and this would result in the theoretical sizes indicated in Table 9. These theo- 

309 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



retical sizes, however, should be modified by not using a wet return less than 2 in. while 
the main supply, g-h, if from the uptake of a boiler, should be made the full size of the 
main, or 3 in. Also the portion of the main k-m should be made 2 in. if the wet return 
is made 2 in. 

Notes on Gravity One-Pipe Air-Vent Systems 

1. Pitch of mains should not be less than l /i in. in 10 ft. 

2. Pitch of horizontal runouts to risers and radiators should not be less than J^ in. 
in 10 ft. Where this pitch cannot be obtained runouts over 8 ft in length should be one 
size larger than called for in the table. 

3. In general, it is not desirable to have a main less than 2 in. The diameter of the 
far end of the supply main should not be less than half its diameter at its largest part. 

4. Supply mains, branches to risers, or risers, should be dripped where necessary. 



TABLE 9. 



PIPE SIZES FOR ONE- PIPE UP-FEED SYSTEM SHOWN 
IN FIG. 1 



PAST OF SYSTEM 


SECTION 

OTPlPE 


RADIATION 
SUPPLIED 
(SQ FT) 


THEORETICAL 
PIPE SIZE 
(INCHES) 


PRACTICAL 
PIPE SIZE 
(INCHES) 


Branches to radiators.. 
Branches to radiators.. 
Riser 
Riser 
Riser 


a to b 
btoc 
c to d 


100 
50 
200 
300 
400 


2 

Ifc 
2 
2iz 
fZ 

Wz 


2 

IJi 
2 

2M 
2H 


Riser 
Riser 

Branch to riser 
Supply main 


dtoe 
etof 
/tog 
g to h 


500 
600 
600 
600 


3 
3 
3Ji 
3 


3 
3 

3M 
3 


Branch to supply main 
Dry return main 
Wet return main 
Wet return main 
Wet return main 


htoj 
ftok 
ktom 
mton 
ntop 


600 
600 
600 
600 
600 


2^ 
IK 

1 
1 


3 
2 
2 
2 
2 




FIG. 1. RISER, SUPPLY 

MAIN AND RETURN MAIN 

OF ONE-PIPE SYSTEM 



From Boiler or 
Source of Supply 




TWO-PIPE GRAVITY AIR-VENT SYSTEMS 

The method employed in determining pipe sizes for two-pipe gravity 
air-vent systems is similar to that described for one-pipe systems except 
that the steam mains never carry radiator condensation. The drop 
allowable per 100 ft of equivalent run is obtained by taking the equiva- 
lent length to the farthest radiator as double the actual distance, and 
then dividing the allowable or desired total drop by the number of 
hundreds of feet in the equivalent length. Thus in a system measuring 
400 ft from the boiler to the farthest radiator, the approximate equivalent 
length of run would be 800 ft. With a total drop of ^ Ib the drop per 



100 ft would be ^~ or 

o 



Ib; therefore, Column D would be used for all 



steam mains where the condensation and steam flow in the same direc- 
tion. If a total drop of J^ Ib is desired, the drop per 100 ft would be J^ Ib 

310 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 

and Column B would be used. If the total drop were to be 1 Ib, the drop 
per 100 ft would be Y% Ib and Column E would be used. 

For mains and riser runouts that are not dripped, and for radiator 
runouts where in all three cases the condensation and steam flow in 
opposite directions, Column I should be used, while for the steam risers 
Column H should be used unless the drop per 100 ft is J^ Ib or \<& Ib, 
when Columns B or C should be substituted so as not to exceed the drop 
permitted. 

On an overhead down-feed system the main steam riser should be 
sized by reference to Column H, but the down-feed steam risers sup- 
plying the radiators should be sized by the appropriate Columns B through 
G, since the condensation flows downward with the steam through them. 
The riser runouts, if pitched down toward the riser as they should be, are 
sized the same as the steam mains, and the radiator runouts are made the 
same as in an up-feed system. 

In either up-feed or down-feed systems the returns are sized in the 
same manner and on the same pressure drop basis as the steam main ; the 
return mains are taken from Columns 0, R, U, X, or A A according to the 
drop used for the steam main; and the risers are sized by reading the 
lower part of Table 8 under the column used for the mains. The hori- 
zontal runouts from the riser to the radiator are not usually increased on 
the return lines although there is nothing incorrect in this practice. The 
same notes apply that are given for one-pipe gravity systems. 

TWO-PIPE VAPOR SYSTEMS 

While many manufacturers of patented vapor heating accessories have 
their own schedules for pipe sizing, an inspection of these sizing tables 
indicates that in general as small a drop as possible is recommended. . The 
reasons for this arer^l) to have the condensation return to the boiler by 
gravity, (2) to obtain a more uniform distribution of steam throughout 
the system, especially when it is desirable to carry a moderate or low 
fire, and (3) because with large variation in pressure the value of gradu- 
ated valves on radiators is destroyed. 

For small vapor systems where the equivalent length of run does not 
exceed 200 ft, it is recommended that the main and any runouts to risers 
that may be dripped should be sized from Column D, while riser runouts 
not dripped and radiator runouts should employ Column I. The up-feed 
steam risers should be taken from Column H. On the returns, the risers 
should be sized from Column U (lower portion) and the mains from 
Column U (upper portion). It should again be noted that the pressure 
drop in the steam side of the system is kept the same as on the return side 
except where the flow in the riser is concerned. 

On a down-feed system the main vertical riser should be sized from 
Column JET, but the down-feed risers can be taken from Column D al- 
though it so happens that the values in Columns D and H correspond. 
This will not hold true in larger systems. 

For vapor systems over 200 ft of equivalent length, the drop should not 
exceed K Ib to J Ib, if possible. Thus, for a 400 ft equivalent run the 
drop per 100 ft should be not over y% Ib divided by 4, or J^ Ib. In this 
case the steam mains would be sized from Column B ; the radiator and 

311 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

undripped riser runouts from Column /; the risers from Column B, 
because Column H gives a drop in excess of J^ Ib. On a down-feed 
system, Column B would have to be used for both the main riser and the 
smaller risers feeding the radiators in order not to increase the drop over 
^2 Ib. The return risers would be sized from the lower portion of Column 
and the dry return main from the upper portion of the same column, 
while any wet returns would be sized from Column^. The same pressure 
drop is applied on both the steam and the return sides of the system. 

Notes on Vapor Systems 

1. Pitch of mains should not be less than %'m.m 10 ft. 

2. Pitch of horizontal runouts to risers and radiators should not be less than 3^ in. 
in 10 ft. Where this pitch cannot be obtained runouts over 8 ft in length should be one 
size larger than called for in the table. 

3. In general it is not desirable to have a supply main smaller than 2 in., and when the 
supply main is 3 in. or over at the boiler or pressure reducing valve it should not be less 
than 2J^ in. at the far end. 

4. When necessary, supply main, supply risers, or branches to supply risers should be 
dripped separately into a wet return. The drip for a vapor system- may be connected 
into the dry return through a thermostatic drip trap. 

VACUUM SYSTEMS 

Vacuum systems are usually employed in large installations and have 
total drops varying from % to % Ib. Systems where the maximum 
equivalent length does not exceed 200 ft preferably employ the smaller 
pressure drop while systems over 200 ft equivalent length of run more 
frequently go to the higher drop, owing to the relatively greater saving in 
pipe sizes. For example, a system with 1200 ft longest equivalent length 
of run would employ a drop per 100 ft of J^ Ib divided by 12, or ^4 Ib. 
In this case the steam main would be sized from Column C, and the risers 
also from Column C (Column H could be used as far as critical velocity is 
concerned but the drop would exceed the limit of J^4 Ib). Riser runouts, 
if dripped, would use Column C but if undripped would use Column 7; 
radiator runouts, Column /; return risers, lower part of Column 5; 
return runouts to radiators, one pipe size larger than the radiator trap 
connections. 

Notes on Vacuum Systems 

1. It is not generally considered good practice to exceed H-rt> drop per 100 ft of 
equivalent run nor to exceed 1 Ib total pressure drop in any system. 

2. Pitch of mains should not be less than J in. in 10 ft. 

3. Pitch of horizontal runouts to risers and radiators should not be less than J^ in. 
in 10 ft. Where this pitch cannot be obtained runouts over 8 ft in length should be one 
size larger than called for in the table. 

4. In general it is not considered desirable to have a supply main smaller than 2 in. 
When the supply main is 3 in. or over, at the boiler or pressure reducing valve, it should 
not be less than 2% in. at the far end. 

5. JWhen necessary, the supply main, supply riser, or branch to a supply riser should 
be dripped separately through a trap into the vacuum return. A connection should not 
be made between the steam and return sides of a vacuum system without interposing a 
trap to prevent the steam from entering the return line. 

6. Lifts should be avoided if possible, but when they cannot be eliminated they 
should be made in the manner described in Chapter 15 under Up-Feed Vacuum Systems. 

312 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 

ATMOSPHERIC SYSTEMS 

The sizing of the supply and return piping on atmospheric systems is 
practically identical with the sizing used for vacuum systems and the 
same notes appty, except that no lift can be made in the return line. 

SUB-ATMOSPHERIC SYSTEMS 

Any properly pitched, correctly sized vacuum system without a'lift 
except at the vacuum pump may be used as a sub-atmospheric system 
when the proper equipment is substituted for the ordinary vacuum 
pump, traps, and controls. On new systems manufacturers usually 
recommend a drop on the steam line of between J and } o lb for the total 
run, and suggest adding 25 ft to the total equivalent length of run to 
insure that the steam gets through to the last radiator. 

The same notes apply to these systems as for vacuum systems, except 
that no lifts can be made In the returns. 

ORIFICE SYSTEMS 

The orifice systems can be operated with any piping system suitable 
for vacuum operation, according to experienced designers. Because these 
systems vary considerably in detail, it is advisable to consult the manu- 
facturer of the particular system contemplated for recommendations. 

The same notes apply to these systems as to vacuum systems, except 
that lifts cannot be made in the returns of orifice systems if a vacuum 
pump is used. 

HIGH PRESSURE STEAM 

When steam heating systems are supplied with steam from a high 
pressure plant, one or more pressure-reducing valves are used to bring the 
pressure down to that required by the heating system. It has been con- 
sidered good practice to make the pressure reductions in steps not to 
exceed 50 lb in each case. For example, in reducing from 100-lb gage to 
2-lb gage, two pressure reducing valves would be used, the first reducing 
the pressure from 100-lb gage to 50 lb and the second reducing the pressure 
from 50-lb gage to 2-lb gage. Valves are available that will reduce 100 lb 
in one step, and it is questionable whether two valves are now required 
for initial pressures of 150 lb or less. 

The pressure-reducing valve, or pressure-regulator as it is sometimes 
termed, has ratings which vary 200 to 400 per cent. Some of these 
ratings are based on arbitrary steam velocities through the valve of 
5,000 to 10,000 fpm and it is assumed that the valve when wide open has 
the same capacity as the pipe on the inlet opening of the valve. At times 
it is considered desirable to keep the steam velocity in the high pressure 
section of the piping and the low pressure section constant. The velocity 
through the valve port is obviously a function of the pressure drop across 
the valve. It is well known that steam flowing through an orifice increases 
its velocity until the pressure on the outlet side is reduced to 58 per cent 
of the absolute pressure on the inlet side, and that with further reduction 
of pressure on the outlet side little change in velocity will be obtained. 
As practically all pressure-reducing valves used for steam heating work 

313 



HEATING VENTIIIATING AIR CONDITIONING GUIDE 1938 



lower the steam pressure to less than 58 per cent of the inlet pressures, 
only the maximum velocity through such valves need be considered. 
If it is assumed that the valve, when fully open, has an area equal to 
that of the inlet pipe size, that the steam is flowing into a pressure less 
than 58 per cent of the initial pressure, that the orifice efficiency is approx- 
imately 70 per cent, and that 20 per cent more is allowed for a factor of 
safety, then the pressure reducing valves will have the working capacities 
shown in Table 10. If the valve, when fully open, does not give an orifice 
area equal to that of the pipe on the inlet side, then the capacities will be 
proportional to the percentage of opening secured, taking the pipe area 
as 100 per cent. More frequently, difficulty is encountered from the use 
of pressure reducing valves which are too large in size instead of being 

TABLE 10. CAPACITIES OF PRESSURE-REDUCING VALVES 
(100-LB GAGE DOWN TO ANY PRESSURE 52 LB OR LESS) 



INLBT NOMINAL 
PIPS DIAMBTBB 
(INCHES) 


POIWDS STEAM 
PER HOUR 
AT 100-Ls GAGK 


EQUIVALENT DIRECT 
RADIATION SQ FT 
AT^LB 


EQUIVALENT DIRECT 
RADIATION SQ FT 
AT^LB 


M 


866 


3,464 


2,598 


a/ 


1,576 


6,304 


4,728 


1 


2,459 


9,836 


7,377 


IK 


4,263 


17,052 


12,689 


1H 


5,808 


23,232 


17,424 


2 


9,564 


38,256 


28,692 


2Ji 


13,623 


54,492 


40,869 


3 


21,041 


84,104 


63,123 


3Ji 


28,213 


112,852 


84,039 


4 


36,285 


145,140 


108,855 


5 


56,971 


227,884 


170,913 


6 


82,336 


329,344 


247,008 



Formula: 



where 



A X V X 3600 X .50 
144 X 3.88 



pounds per hour passed by orifice. 



A = area of inlet pipe, square inches. * 

V = velocity of steam through orifice (approximately 870 fps). 
50 = 70 per cent efficiency of orifice less 20 per cent for factor of safety. 
144 = square inches in 1 sq ft. 
3600 = seconds in one hour. 
3.88 ** cubic feet per pound at 100-lb gage. 

too small. Where valves are large in size, the valve tends to work close 
to the seat, causing it to cut out in a relatively short time, as well as 
being noisy in operation. 

Most exact regulation of pressure on steam heating systems is secured 
from diaphragm-operated valves controlled by a pilot line from the low 
pressure pipe, taken off the low pressure main at least 15 ft from the 
reducing valve. The reducing valves operating on the proportional- 
reduction principle will give a variation of steam pressure on the low 
pressure side if the initial pressure varies between considerable limits. 
The so-called dead-end valve is used for reduced pressures where the line 
has not sufficient condensing capacity at all times to condense the leakage 
that might occur with the ordinary valve. Single-disc valves do not give 
as close regulation as double-disc valves, but the single disc is preferable 
where dead-end valves are necessary, such as on short runs to thermo- 

314 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 

statically controlled hot water heaters, central fan heating units and 
unit heaters. 

The correct installation (Fig. 2) of a pressure-reducing valve includes 
a pressure-reducing valve with a gate valve on each side, a by-pass con- 
trolled by a globe valve, a pressure gage on the low pressure side, and a 
safety valve on the low pressure main at some point, usually within a 
reasonable distance of the pressure-reducing valve. Pressure-reducing 
valves should have expanded outlets for sizes greater than 2 in. Where 
the steam main is of still larger diameter than the expanded outlet, and in 
cases where straight valves are used, an increaser is placed close against 
the outlet of the valve to reduce the velocity immediately after passing 
through the valve. Strainers are recommended on the inlets of all 
pressure-reducing valves. A pressure gage may be located on the high- 
pressure line near the valve if desired. 

Owing to the large variation in steam demand on the average heating 
system , it is generally advisable to use two pressure-reducing valves con- 
Less trouble from expansion leaks will occur when the bypass 
valve is on the same center line as the pressure reducing valve 

Bypass (same size as high ^ Globe valve 

pressure supply line) ^ ^faj^^S* fety valve 

Pressure gage, 
if desired 



High pressure steam 

Drip' , , ^ 

Pressure reducing valve ^ Pilot line 

FIG. 2. TYPICAL PRESSURE-REDUCING VALVE INSTALLATION 

nected in parallel. One valve should be large enough for the maximum 
load and the other should have a diameter approximately half that of the 
first. The smaller valve can be used most of the time, for it will give 
much better regulation than the larger one on light or normal loads. 

Control Valves 

Gate valves are recommended in all cases where service demands that 
the valve be either entirely open or entirely closed, but they should never 
be used for throttling. Angle globe valves and straight globe valves 
should be used for throttling, as done on by-passes around pressure 
reducing valves or on by-passes around traps. 

EXPANSION IN STEAM AND RETURN LINES 

Because all steam and return lines expand and contract with changes 
in temperature, provision should be made for such movement. The 
expansion in steam supply pipes is normally taken at 1J to 1^ in. per 
100 ft and in return lines at one-half or two-thirds of this amount. It 
may be calculated accurately if the temperature rise and fall can be 
determined with reasonable certainty (Chapter 18). The temperature 
at the time of erection often has a greater expansion effect on piping than 
the temperature in the building after it has been put into service. 

315 




HEATING VENTIIATING AIR CONDITIONING GUIDE 1938 

Expansion may be taken care of by any, or all, of three different 
methods, namely, (1) the spring in the pipe including offsets and expan- 
sion bends, (2) the turning of the pipe on its threads and swing joints, and 
(3) the use of expansion joints. 

By the first scheme, which is the most popular method where space 
permits, the pipe is offset, or broken, around rooms or corners, and is hung 
so that the spring in the pipe at right angles to the expansion movement 
is sufficient to absorb the expansion. If conditions do not lend themselves 
to this treatment, regular expansion bends of the U or offset type may be 
used. In tight places such as pipe tunnels the expansion joint is pre- 
ferable. See additional material on pipe expansion bends in Chapter 18. 

On riser runouts and radiator runouts the swing joint is used almost 
without exception. On high vertical risers the pipes may be reversed 
every five to ten stories; that is, the supply is carried over to the adjacent 
return riser location and the return riser is run over to the former supply 
riser location, thus making horizontal offsets in each line. Corrugated 
copper expansion joints also are used on risers but must be made acces- 
sible in case future replacement becomes necessary. 

PIPING CONNECTIONS AND DETAILS 

Piping connections may be classified into two groups: first, those 
suitable for any system of steam heating; second, those devised for certain 
systems which cannot be satisfactorily applied to any other type. There 
are also various details that apply to piping on the steam side which 
cannot be used on the returns. An installation that is designed and sized 
correctly and installed with care may be rendered defective by the use of 
improper connections, such as runouts that do not allow for expansion, 
thermostatic traps unprotected from scale, pressure-reducing valves 
without strainers, and lack of drips at required points. 

BOILER CONNECTIONS 
Supply 

Boiler headers and connections have the largest sizes of pipe used in a 
system. Cast-iron, horizontal-type, low pressure heating boilers usually 
have several tapped outlets in the top, the manufacturers recommending 
their use in order to reduce the velocity of the steam in the vertical up- 
takes from the boiler and to permit entrained water to return to the 
boiler instead of being carried over into the steam main where it must be 
cared for by dripping. Steel heating boilers usually are equipped with 
only one steam outlet but many engineers believe that better results are 
obtained by specifying that such boilers have two. The second outlet, 
usually located 3 or 4 ft back of the regular one, reduces the velocity 
50 per cent in the steam uptake. 

Fig. 3 shows a type of boiler connection that was used for many years 
and one with which some boilers are now piped. The uptakes are carried 
as high as possible, turned horizontally and run out to the side of the 
boiler and then are connected together into the main boiler runout which 
drops into the^top of the boiler header through a boiler stop valve. No 
drips are provided on this type of runout except a very small one which 
is sometimes installed on the boiler side of the stop valve. Fig. 4 shows a 

316 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 

type of boiler connection which is regarded as superior to that shown in 
Fig. 3 and which is the type illustrated in the system diagrams in Chapter 
15. This type is similar to that shown in Fig. 3 except that the horizontal 
branches from the uptakes are connected into the main boiler runout, and 
the steam is carried toward the rear of the boiler. The branch to the 
building or boiler header is taken off behind the last horizontal boiler con- 
nection. At the rear end of this main runout, a large size drip, or balance 
pipe, is dropped down into the boiler return, or into the top of the Hart- 
ford Loop, which is described in a following paragraph. As a result, any 
water carried over from the boiler follows the direction of steam flow 



Reducing ell 
Uptake- 




Main runout to 

building or 

header 

-Drip and balance pipe 
Water line 
Hartford return connection 

Main wet return 



FIG. 3. OLD STYLE STANDARD BOILER 
CONNECTIONS 



FIG. 4. APPROVED METHOD OF BOILER 
CONNECTIONS 



toward the rear and is discharged into the rear drip, or balance pipe, 
without being carried over into the system. 

Return 

Cast-iron boilers are generally provided with return tappings on both 
sides, but steel boilers often are equipped with only one return tapping. 
A boiler with side return tappings will usually have a more effective cir- 
culation if both tappings are used. Check valves generally should not be 
used on the return connection to steam heating boilers from one and two 
pipe gravity systems because they are not always dependable inasmuch 
as a small piece of scale or dirt lodged on the seat will hold the tongue open 
and make the check useless. These valves also offer a certain amount of 
resistance to the returns coming back to the boiler, and in gravity systems 
will raise the water line in the far end of the wet return several inches 3 . 
However, if check valves are omitted and the steam pressure is raised 
with the boiler steam valve closed, the water in the boiler will be blown 
out into the return system with the accompanying danger of boiler 
damage. These objections are largely overcome with the Hartford 
return connection. 



*See method of calculating height above water line for gravity one-pipe systems in Chapter 15 

317 








mains. The a ^ 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 



boiler and the horizontal main or runout is compensated for by the use of 
reducing ells (Figs. 3 and 4). 

The following example illustrates the sizing of the boiler connections 
shown in Fig. 6. 

Example 4. Determine the size of boiler steam header and connections (Fig. 6) if 
there are three boilers, two to carry 50 per cent of the load each, and the third to be used 
as a spare. The steam mains are based on J^-lb drop per 100 sq ft of equivalent direct 
radiation CEDR). 



6,000 sq ft 


2,000 sq ft 


] 
D 


,000 sq ft 3,000 sq ft 




A_ D 
_ >ft. D 




E y* F 






Header 



18,000 



Solution: 



Water line 



FIG. 6. BOILER STEAM HEADER AND CONNECTIONS 
Size of Boiler Header 



WHEN 
OPERATING 
ON BOILERS 


LOJLD ON VARIOUS PORTIONS or HKAJDHS 


MAXIMUM 
LOAD 


A 


B 


C 


D 


E 


F 


Nos. 1 and 2 
Nos. 2 and 3 
Nos. 3 and 1 


6000 
6000 
6000 



6000 



2000 
8000 
2000 


4000 
2000 
2000 


3000 
3000 
3000 


3000 
3000 
3000 


6000 
8000 
6000 


Max. Load 


6000 


6000 


8000 


4000 


3000 


3000 


8000 



8000 sq ft @ H Ib per 100 ft - 6 in. main. (See Table 7.) 

Size of Boiler Runouts 



The three runouts 

8000 



= 2667 sq ft each @ >g Ib per 100 ft = 4 in. pipe. 



Hi, H*, Hi = 2667 sq ft each % Ib per 100 ft = 4 in. pipe 4 (See Table 7). 
/i, Js, Ji - 5333 sq ft each @ J Ib per 100 ft = 5 in. pipe 4 (See Table 7). 
1, jRTs, K* = 8000 sq ft each @ }g Ib per 100 f t = 6 in. pipe 4 (See Table 7). 

The uptakes from the boiler probably would be 6 in. pipe with a 6 in. X 4 in. reducing 
ell at top. 

*Note. As Ki, Ks, K all carry 8000 SQ ft and are 6 in. pipe, the whole runout including Ji, 7s and Ji 
and Hi, Hi and Hz and the leads from the boiler headers to the main steam header would also be made 
6 in. pipe. 

319 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

Return connections to boilers in gravity systems are made the same 
size as the return main itself. Where the return is split and connected to 
two tappings OR the same boiler, both connections are made the full size 
of the return line. Where two or more boilers are in use, the return to 
each may be sized to carry the full amount of return for the maximum load 
which that boiler will be required to carry. Where two boilers are used, 
one of them being a spare, the full size of the return main would be 
carried to each boiler, but if three boilers are installed, with one spare, the 
return line to each boiler would require only half of the capacity of the 
entire system, or, if the boiler capacity were more than one-half the entire 
system load, the return would be sized on the basis of the maximum 
boiler capacity. As the return piping around the boiler is usually small 
and short, it should not be sized to the minimum. 



inout. 



Wall line 



Swing 



"Miiii I hi 1 1 il Mull H 1 1 



^^ Runout below floor 
PLAN 




^Runout below floor 
ELEVATION 

FIG. 7. ONE-PIPE RADIATOR CONNECTIONS 

With returns pumped from a vacuum or receiver return pump, the size 
of the line may be calculated from the water rate on the pump discharge 
when it is operating, and the line sized for a very small pressure drop, the 
size being obtained from the Chart for Pressure Drop for Various Rates of 
Flow of Water, Fig. 3, Chapter 43. The relative boiler loads should be 
considered, as in the case of gravity return connections. 

Radiator Connections 

Radiator connections are important on account of the number of 
repetitions which occur in every heating installation. They must be 
properly pitched and they must be arranged to allow not only for move- 
ment in the riser but, in frame buildings, for the shrinkage of the building. 
In a three story building this sometimes amounts to 1 in. or more. The 
simplest connection is that for the one-pipe system where only one radia- 
tor connection is necessary. Where the radiator runouts are located on 
the ceiling or under the floor, sufficient space usually is available to make 

320 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 





FIG. 8. CONNECTIONS TO 
STEAM-TYPE RADIATOR 
FOR Two- PIPE SYSTEM 



FIG. 9. TOP AND BOTTOM 

OPPOSITE END RADIATOR 

CONNECTIONS 




FIG. 10. TOP AND 

BOTTOM RADIATOR 

CONNECTIONS 



a good swing joint with plenty of pitch, but where the runouts must come 
above the floor the vertical space is small and the runouts can project out 
into the room only a short distance. Fig. 7 illustrates two satisfactory 
methods of making runouts on a one-pipe gravity air vent system of 
either the^up-feed or down-feed type, the runout below the floor being 
indicated in full lines and the runout above the floor in dotted lines. 
Sometimes it is necessary to set a radiator on pedestals, or to use high 
legs, in order to obtain sufficient vertical distance to accommodate above- 
the-floor runouts. Particular attention must be given to the riser expan- 
sion as it will raise the runout and thereby reduce the pitch. 

Similar connections for a two-pipe system of the gravity air vent type 
are illustrated in Fig. 8 for the old steam type radiator. If the water 
type is used, the supply tapping is at the top instead of at the bottom, the 
runouts otherwise remaining as shown in Fig. 8. A satisfactory type 
of radiator connection for atmospheric, vapor, vacuum, sub-atmos- 
pheric, and orifice systems of both the up-feed and down-feed types is 
shown in Fig. 9. 

While short radiators, not exceeding 8 to 10 sections, may be supplied 
and returned from the same end as indicated in Fig. 10, the top-and- 
bottom-opposite-end method is to be preferred in all cases where it can be 
used. On down-feed systems of the atmospheric, vapor, vacuum, sub- 
atmospheric, and orifice types, the bottom of the supply riser must be 
dripped into the return somewhat as illustrated in Fig. 11. On up-feed 
systems of the vapor and atmospheric types, where radiators in the 
basement are located below the level of the steam main, the drop to the 
radiator is dripped into the wet return and an air line is used to vent the 
return radiator connection into an overhead return line, as illustrated in 
Fig. 12. When the radiator stands on the floor below the main, the drip 





ttetpodaufflft 



FIG. 11. TOP AND BOTTOM 

OPPOSITE END RADIATOR 

CONNECTIONS 



FIG. 12. CONNECTIONS 

TO RADIATOR HUNG 

ON WALL 

321 



FIG. 13. CONNECTING 

DROP RISER DIRECT 

TO RADIATOR 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

on the steam branch down to the radiator may be omitted if an overhead 
valve, as shown in Fig. 13, is used. This method is also suitable for 
vacuum, sub-atmospheric, and orifice systems. 

Converter Connections 

Convectors often are installed without control valves, a damper being 
used to shut off the flow of air to retard the heat transfer from the con- 
vector even though it is still supplied with steam. The piping connec- 
tions for a convector with the inlet and outlet at the same end are shown 
in Fig. 14. There is no valve on the steam side but there is a thermostatic 
trap on the return. The damper for control is shown immediately above 
the convector. This piping is suitable for atmospheric, vapor, vacuum, 





FIG. 14. CONVECTOR CON- 
NECTIONS SAME END 



FIG. 15. HORIZONTAL 

FIN-TYPE HEATING 

UNIT 



FIG. 16. HEATING UNIT 
VALVES BEHIND GRILLE 




FIG. 17. HEATING UNIT 

WITH VALVES IN 

BASEMENT 




it radiator 




FIG. 18. FIN-TYPE HEAT- 
ING UNIT IN CABINET 



Dirt pocket 



FIG. 19. PIPING CONNEC- 
TIONS TO INDIRECT 
RADIATORS 



sub-atmospheric, and orifice systems of the up-feed type. A similar unit 
with connections on opposite ends ^and suitable for the same systems is 
shown in Fig. 15. This unit has no damper but requires a valve on the 
steam connection for control. When valves must be located so as to be 
accessible from the supply air grille, the arrangement usually takes the 
form indicated in Fig. 16. A convector located in the basement and 
supplying air to a room on the floor above may be piped as pictured in 
Fig. 17 for all systems except gravity one-pipe or two-pipe systems. 
Convectors with damper control, installed in cabinets or under window 
sills, usually are connected as shown in Fig. 18. 

Vapor systems with heating units in the basement where the returns 
are dry would be treated as in Fig. 19. Similar heating units where a wet 
return is available would be connected as shown in Fig. 20. If the dry 

322 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 



return were on a vacuum, atmospheric, sub-atmospheric or orifice system, 
the treatment would be identical. 

On all heating units it is important to use a nipple the full size of the 
outlet and to reduce the pipe size to the normal return size required, by 
the use of a reducing ell, as indicated in Fig. 21. 

Pipe Coil Connections 

Pipe coils, unless coupled in a correct manner, often give trouble from 
short circuiting and poor circulation. The method of connecting shown 
in Fig. 22 is suitable for atmospheric, vapor, vacuum, sub-atmospheric, 
and orifice systems. 



Indirect radiator 



is point to be at least 
24 in. above boiler water line 




FIG. 20. TYPICAL PIPING CON- 
NECTIONS TO CONCEALED HEAT- 
ING UNITS WITH WET RETURNS 



Reducing ell 



Thermostatic trap 



To return line 
beyond blast traps 

To blast trap 



Check valve 



FIG. 21. HEATING UNIT RETURN CON- 
NECTION WITH SEPARATE AIR LINE 



Indirect Air Heater Connections 

Heating units for central fan systems have simple connections on the 
steam side. The steam main is carried into the fan room and has a 
single branch tapped off for each row of heating units. Each of these 
main branches is split into as many connections as need be made to each 
row, governed by tihe number of stacks and the width of the stacks. Each 
stack must have at least one steam connection, and wide stacks are more 
evenly heated with two steam connections, one at each end. 

323 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Typical connections to manifold 
coils of not over 8 pipes 




Typical connections to manifold 
coils having more than 8 pipes 



Dirt pocket 

RetunvjTU 

K ODVfrT 

Dirt pocket Jl 

R-+,,m^y 



FIG. 22. TYPICAL PIPE COIL CONNECTIONS 



The piping shown in Fig. 23 is for small stacks and has the steam con- 
nected at only one end. On the return side all of the returns are collected 
together through check valves and are passed through blast traps which 
are connected to the vacuum return or to an atmospheric return. The air 
from the stacks, in the case illustrated, passes up into a small air line and 
through a thermostatic trap into a line connecting into the return beyond 
the blast trap. 

Where the stacks contain some thirteen or more sections, an auxiliary 
air tapping is made to the lower portion of one of the middle sections, in 
the manner illustrated in Fig. 24, to prevent air collecting at this point. 
Thermostatic control as applied to such heating units in modern practice 




-Valve 



Blast heaters . 



Blast traps - 



Return^ 





FIG. 23. SUPPLY AND RETURN CON- 
NECTIONS FOR HEATING UNITS OF 
CENTRAL FAN SYSTEMS 



FIG. 24. TYPICAL CONNECTIONS TO 

CENTRAL FAN SYSTEM HEATING 

UNITS EXCEEDING 12 SECTIONS 



324 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 



consists of a thermostatic valve located in each main branch from the 
steam line so that each valve will open or close a complete row of stacks 
across the entire face of the heating unit. In such cases the outlet con- 
nections from each stack should be provided with a check valve. The 
stack closest to the outside air intake usually is not equipped with a 
thermostatic valve. A gate valve on the steam pipe to the first coil is 
operated manually to supply steam continuously in freezing weather. 
Good practice demands that the returns be connected in parallel with 
the steam supplies, with a separate steam trap for each bank of coils 
having a separately valved steam supply. This arrangement is illustrated 
in Fig. 23, for blast traps having external thermostatic by-passes and 
integral thermostatic by-passes, respectively. 



Steam main 




FIG. 25. UNIT HEATER CONNECTED TO ONE-PIPE AIR- VENT SYSTEM 

A method of connecting a unit heater to a one-pipe air-vent steam 
heating system is illustrated in Fig. 25. 

PIPE SIZING FOR INDIRECT HEATING UNITS 

Pipe connections and mains for indirect heating units are sized in a 
manner similar to radiators, but the equivalent direct radiation must be 
ascertained for each row of heating unit stacks and then must be divided 
into the number of stacks constituting that row and into the number of 
connections to each stack, 

77 rE> y ^ X (*1 EC) (2 X (*1 *t) fn\ 

EDR 55.2 X 240 2208 (3) 

where 

EDR = equivalent direct radiation, square feet. 
Q = volume of air, cubic feet per minute. 

fe = the temperature of the air entering the row of heating units under con- 
sideration, degrees Fahrenheit. 

ft = the temperature of the air leaving the row of heating units under considera- 
tion, degrees Fahrenheit. 
60 = the number of minutes in one hour. 
55.2 = the number of cubic feet of air heated 1 F by 1 Btu. 
240 = the number of Btu in 1 sq ft of EDR. 

325 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



Example 6. Assume that the heating units shown in Fig. 26 are handling 50,000 cfm 
of air and that the rise in the first row is from to 40 F f in the second row from 40 to 
65 F, and in the third row from 65 to 80 F. What is the load in EDR on each supply 
and return connection? 



Gate valves N 



/Thermostatic valves 




FIG. 26. TYPICAL PIPING FOR ATMOSPHERIC AND VACUUM SYSTEMS WITH 
THERMOSTATIC CONTROL (CENTRAL FAN SYSTEM) 



Solution. For row 1, 



_ 50.000 X (40 - 0) _ 
R -- 2208 -- 90SS Sq ft 



For row 2, 



R 



50,000 ^ (65 - 40) 



For row 3, 






=3 397s< 1 ft. 



Each row of heating units consists of four stacks and each stack has two connections 
so that the load on each stack and each connection of the stack is as follows: 



Row 


TOTAL LOUD 
(EDR) 


STACK LOAD* 
(EDR) 


CONNECTION LoADb 
(EDR) 


1 


9058 


2265 


2265 or 1132 


2 


5661 


1415 


1415 or 708 


3 


3397 


S49 


849 or 425 



One quarter of total row load. 

fcOne half of stack load If two steam connections are made; otherwise, same as stack load. 

326 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 



The pipe sizes would then be based on the length of the run and the pressure drop 
desired, as in the case of radiators. It generally is considered desirable to place the in- 
direct heating units on a separate system and not on supply or return lines connected to 
the general heating system. 

DRIPPING 

Any steam main in any type of steam heating system may be dropped 
to a lower level without dripping if the pitch is downward with the steam 
flow. Any steam main in any heating system can be elevated if dripped 
(Fig. 27). Steam mains also may be run over obstructions without a 
change in level if a small pipe is carried below the obstruction to care for 



r 



Reoueing coupUng-^y > 

U 

FIG. 27. DRIPPING MAIN 

WHERE IT RISES TO 

HIGHER LEVEL 





Haixlhote 



Plug tee for 



FIG. 28. LOOPING MAIN 
AROUND BEAM 



FIG. 29. LOOPING DRY 

RETURN MAIN AROUND 

OPENING 



r 



45elbow N 




Acceptable method 



Main 
Preferred method 




FIG. 30. METHODS OF 
TAKING BRANCH FROM 

MAIN 



To find length Omutopty A 
by constant for angleB 

FIG. 31. CONSTANTS FOR 

DETERMINING LENGTH 

OFFSET PIPE 




FIG. 32. DIRT POCKET 
CONNECTION 



the condensation (Fig. 28). Return mains may be carried past doorways 
or other obstructions by using the scheme illustrated in Fig. 29 ; in vacuum 
systems it is well to have a gate valve in the air line. 

Branches from steam mains in one-pipe gravity steam systems should 
use the preferred connection shown in Fig. 30, but where radiator condensa- 
tion does not flow back into the main the acceptable method shown in the 
same figure may be used. This acceptable method has the advantage of 
giving a perfect swing joint when connected to the vertical riser or radia- 
tor connection, whereas the preferred connection does not give this swing 
without distorting the angle of the pipe. Runouts from the steam main 
are usually made about 5 ft long to provide flexibility for movement in 
the main. 

Offsets in steam and return piping should preferably be made with 

327 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

90-deg ells but occasionally fittings of other angles are used, and in such 
cases the length of the diagonal offset will be found as shown in Fig. 31. 

Dirt pockets, desirable on all systems employing thermostatic traps, 
should be so located as to protect the traps from scale and muck which 
will interfere with their operation. Dirt pockets are usually made 8 in. 
to 12 in. deep and serve as receivers for foreign matter which otherwise 
would be carried into the trap. They are constructed as shown in Fig. 32. 

On vapor systems where the end of the steam main is dripped down 
into the wet return, the air venting at the end of the main is accomplished 
by an air vent passing through a thermostatic trap into the dry return 
line as shown in Fig. 33. On vacuum systems the ends of the steam mains 
are dripped and vented into the return through drip traps opening into 
the return line. The same method may be used in atmospheric systems. 
A float type trap is preferable to a thermostatic trap for dripping steam 
mains and large risers. If thermostatic traps are used a cooling leg 



N Dry return 





FIG. 33. DRIPPING END FIG. 34. DRIPPING END FIG. 35. DRIPPING HEEL 

OF MAIN INTO WET OF MAIN INTO DRY OF RISER INTO DRY 

RETURN RETURN RETURN 

(Fig. 34) should always be provided. The cooling leg is for cooling the 
condensation sufficiently before it reaches the trap so the trap will not be 
held shut by too high a temperature. On down-feed systems of atmos- 
pheric, vapor, and vacuum types, the bottom of the steam risers are 
dripped in the manner shown in Fig. 35. On large systems it is desirable 
to install a gate valve in the cooling leg ahead of the trap. 



PROBLEMS IN PRACTICE 

1 What factors determine the size of steam piping and the allowable limit 
of capacity? 

Factors which determine the size of steam piping are the desired initial pressure and the 
allowable drop in pressure which is permissable to maintain a pressure in the farthest 
radiator. The length of run in sizing piping is important and it is generally considered 
as the distance along the piping from the source of steam supply to the farthest radiator, 
with allowances for resistance of elbows and valves expressed in terms of equivalent 
length. 

2 "When the size of pipe is still undetermined, what arbitrary percentage is 
usually added to the actual length to obtain the equivalent length? 

Usually 100 per cent; in other words, the actual length is doubled to allow for the added 
drop produced by the valves, tees, elbows, and other fittings. 

328 



CHAPTER 16. PIPING FOR STEAM HEATING SYSTEMS 



3 What are the major factors to I>e considered in determining the flow of 
htcatu in pipes? 

a. The initial steam pressure available and the total pressure drop allowable between the 
source of steam supply and the end of the return system. The pressure drop should 
never exceed one half of the initial pressure. 

b. The maximum steam velocity allowable. When condensate is flowing against the 
steam, the velocity must not be so great as to produce water hammer, or hold up 
water in parts of the system until the steam flow is reduced sufficiently to permit the 
water to pass. The velocity at which disturbances take place depends upon : 

1. Size of pipe. 

2. Whether pipe is vertical or horizontal. 

3. Pitch or grade of pipe. 

4. Quantity of water flowing against steam. 

c. The equivalent length of run from the source of steam supply to the farthest heating 
unit, with allowance for friction in pipe fittings and valves. 

4 Name three fundamental considerations in designing the piping system 
for steam heating. 

a. Provision for the distribution of suitable quantities of steam to the various heating 
units. 

b. Provision for the return of condensate from the radiators and piping to the boiler. 

c. Provision of means for expelling air from the radiators and piping. 

5 Why is the proper reaming of the ends of pipe necessary? 

The capacities of pipes depend upon the free area available for flow. In cutting^the pipe 
this area may be restricted by a burr, which may decrease the capacity of a pipe more 
than 25 per cent in the smaller pipe sizes. 

6 a. What are the major factors to he considered when selecting a pressure 

reducing valve? 

b. How should such valve he installed? 

a. The initial pressure of the steam must be considered along with the desired reduced 
pressure. The connected load to be supplied must be known in square feet of equiva- 
lent direct radiation or in pounds of steam per hour. For operation with a continuous 
load, a semi-balanced or double-seated valve operated by a diaphragm gives good 
results. Where the load is intermittent, as in process work or with thermostatically 
controlled blast heaters, a so-called dead end or single-seated valve should be used. 

b. The pressure reducing valve should be installed in a horizontal line with a gate valve 
on each side, and with a by-pass operated by a valve. The pressure balancing pipe 
from the diaphragm chamber should be connected into the top or side of the low 
pressure main not less than 15 ft from the reducing valve. 

7 What is the usual expansion allowance and how it is compensated for in 
heating system supply risers? 

The expansion of low pressure steam piping is normally taken as 1J4 to IJi in. per 100 
ft of pipe. With a five story building a double swing connection between the riser and the 
main will suffice. In buildings between 5 and 10 stories high the riser should be anchored 
near its center and have double swing connections to the main. For taller buildings 
expansion loops or riser offsets are used which are capable of handling a length of riser 
reaching 5 stories in either direction from the joint. The risers are anchored at each 
alternate 5 stories. All radiators must have double swing connections, and those con- 
nected above where the riser is anchored must be given greater pitch to insure their 
having proper grade when the riser is heated. 

329 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

8 Why should all boiler steam supply tappings be used full size? 

In order to operate at low steam velocities so the water in suspension can separate from 
the steam and remain in the boiler. 

9 What is the Underwriters Loop or the Hartford Connection? 

An arrangement of piping on the returns to low pressure boilers wherein the return line 
is raised up yearly to the water line of the boiler and is then dropped back and con- 
nected to the boiler return inlet; the high point is connected by a balanced pipe to the 
steam runout from the boiler on the boiler side of all stop valves. With this loop no 
check valve is required on gravity systems, and water cannot be backed out of the boiler 
and into the return at a point lower than the invert of the pipe at the top of the loop. 

10 What are the important factors in making radiator connections? 

Connections to radiators should be made as direct as possible, of proper size, with ample 
pitch of piping and allowance for expansion. 

11 Why should careful attention be given to proper dripping and drainage 
of steam piping? 

The steam mains and risers must be quickly drained of condensate and where necessary 
vented of air in order to obtain a sufficient supply of steam to the radiators. Proper 
drainage is also necessary to insure a noiseless heating system. 

12 What is the limit of pressure drop usually recommended in a vacuum 
system? 

Not over J^ Ib (2 oz) per 100 ft of equivalent run, and not over 1 Ib total drop. 

13 When steam and condensation are flowing in the same direction, what is 
the maximum total pressure drop which should be used? 

The maximum total pressure drop should not exceed one half of the initial steam pressure. 

14 What does a proper installation of a pressure reducing valve include? 

A strainer in front of the pressure reducing valve; a gate valve in front of the strainer; a 
gate valve after the reducing valve; a by-pass around the two gate valves, strainer, and 
pressure reducing valve; and a globe valve in the by-pass. Sometimes a safety valve on 
the low pressure side and pressure gages on both sides are installed. The high pressure 
line should be dripped just before the high pressure steam enters the pressure reducing 
valve assembly. 

15 Will a pressure reducing valve which is reducing the steam pressure from 
100 Ib gage to 50 Ib gage pass more or less steam than the same valve when 
reducing the steam pressure from 100 Ib gage to 5 Ib gage? 

The valve will pass practically the same volume of steam in each case as the velocity of 
steam flowing through an orifice shows no material increase after the reduced absolute 
pressure has fallen to 58 per cent of the initial absolute pressure. Because of its greater 
density, the weight of steam passed will be greater in the case of the reduction to 50 Ib 
gage. 



330 



Chapter 17 

HOT WATER HEATING SYSTEMS 
AND PIPING 

One- and Two -Pipe Systems, Mechanical Circulation, Cir- 
culators, Iron Pipe and Copper Tube Sizes, Gravity Circula- 
tion, Expansion Tanks, Relief Valves, Installation Details 

THE various forms of hot water heating may be fundamentally classi- 
fied according to motive force, namely, forced circulation or gravity 
flow. Forced circulation is accomplished by the use of centrifugal or 
propeller type pumps which are especially designed for this particular 
type of application. Gravity flow is maintained by the difference in 
weight of the water in the flow and return mains. 

These systems may be further classified as to high or low operating 
water temperatures. Higher water temperatures permit a reduction in 
radiator size. A large temperature differential between the flow and 
return results in smaller pipe sizes as also does the use of forced circulation. 
Light wall copper tubing has recently been introduced to supplement the 
customary black iron piping which has been used for these systems in 
the past. 

Low temperature water(150 to 180 F) is generally that which provides 
a heat emission per square foot of radiation of from 150 to 165 Btu while 
a high temperature water (200 to 220 F) will deliver from 200 to 240 Btu. 

The use of high temperature water in a heating system is desirable as 
the maximum outside temperature ^f or which the system is designed will 
occur for a relatively short time during the average season. The increased 
use of automatic heating equipment with more accurate controls, makes 
it possible to use higher temperatures and smaller heating units without 
sacrificing good design. 

The unit, a square foot of equivalent direct radiation, EDR, has been 
used for many years for rating purposes in both steam and hot water systems, 
but its use, especially in hot water systems, has always resulted in compli- 
cations and confusion. It is the plan of THE GUIDE to eventually eliminate 
this empirical expression and to stibstitute a logical unit based on the Btu. 
The Mb, the equivalent of 1000 Btu and the Mbh, the equivalent of 1000 Btu 
per hour, which have been approved by the A.S.H.V.E. are used in this 
chapter on hot water systems to replace 'the square foot of radiation formerly 
used. 

331 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

In designing a piping arrangement for a hot water heating system, it is 
necessary to observe the fundamental rule that the total friction head in 
any circuit must not exceed the pressure head available for circulating the 
water. It is necessary to size the pipe in any circuit, so that the friction 
loss produced by the movement of a sufficient volume of water to handle 
the heating load will not be greater than the available head. 

In designing a hot water heating system, it is necessary to determine: 

1. The heat losses of the rooms or spaces to be heated. (See Chapter 7.) 

2. The size and type of boiler. (See Chapter 13.) 

3. The location, type, and size of heating units. (See Chapter 14.) 

4. The method of piping. 

5. The type and size of circulating pump (if forced circulation). 

6. Suitable pipe sizes. 

7. The type and size of expansion tank. 

ONE- AND TWO-PIPE SYSTEMS 

Piping systems may be divided into two general types, namely, one- 
pipe and two-pipe systems. These fundamental piping layouts may 
differentiate between up-flow, down-flow and zoned systems. Also the 
type of riser and radiator connection may vary considerably. Zoning is 
important in modern design and it is accomplished by dividing the system 
into a number of circuits and controlling each circuit individually. In a 
two-pipe system the piping is arranged so that the water flows through 
only one radiator during a circuit through the system, so that all radiators 
are supplied with water at practically the same temperature as that in the 
boiler. In some one-pipe systems, the water flows through more than one 
radiator during its circuit. In that case, the first radiator* receives the 
hottest water; the second radiator, somewhat cooler water; the third one, 
still cooler; and so on. As the temperature of the water supplied to a 
radiator is lowered, the size of the radiator must be increased and, con- 
sequently, the total heating surface for a one-pipe system must be greater 
than for a two-pipe system for the same requirements. As the velocity is 
increased in a one-pipe system, the drop in temperature is decreased, so 
that water at a higher average temperature is delivered to the radiators. 
This means that the radiators at the end of the main can be sized on the 
same basis as the radiators at the beginning of the main. If the system is 
correctly designed, the resulting error is less than the variation in calcu- 
lating the heating load for the enclosure. 

By making use of improved devices now available, one-pipe forced 
circulation systems may be calculated by the same procedure described 
later for two-pipe systems. Operation may be obtained as satisfactory as 
with a two-pipe system. 

Two-pipe systems may be divided into two classes, direct return sys- 
tems (Fig. 1), and reversed return systems (Fig. 2). In a direct return 
system the water returns to the heater by a direct route after it has 
passed through its radiator and, as a result, the paths through the three 
radiators shown in Fig. 1 are of unequal lengths, the path through the 
first radiator being the shortest and that through the third radiator, the 

332 



CHAPTER 17. HOT WATER HEATING SYSTEMS AND PIPING 

longest. In a reversed return system, the water returns to the heater by 
an indirect route after it has passed through the radiators, so that the 
paths leading through the three radiators shown in Fig. 2 are practi- 
cally of equal length. 

The reversed return system has an advantage over the direct return 
system in that it is more likely to function satisfactorily even though the 
pipe system is not accurately designed. For example, if in Fig. 2 all pipes 
are of one size, each of the three radiators will receive approximately the 
same quantity of hot water because the three paths are practically of 
equal length, whereas in Fig. 1, if all pipes are of the same size. Radiator 
1 will receive more water than the others because the path through it is 
shorter than those through the other radiators. As a result, Radiator 1 
will be filled with water at a higher average temperature than the re- 
maining two radiators, and will therefore dissipate more heat. To pre- 
vent this unequal distribution of heat it is necessary to throttle the paths 
through Radiators 1 and 2 so that the friction heads of the three paths are 
equal when each radiator receives its proper quantity of water. 

The two-pipe direct return system, with its inherent lack of balance, 
is the least satisfactory type of piping possible, yet is the most widely used. 



FIG. 1. A DIRECT RETURN SYSTEM 



J 







m, 
1 


ni 

i, 


til, 

i 










4 




1 








H 


_J 









FIG. 2. A REVERSED RETURN SYSTEM 



The modern applications of automatic heating require a system to be very 
nearly in balance so that uniform distribution of heat will be obtained. 

Two-pipe systems must be balanced first by calculation and then by 
test after the plant is in operation. Unbalanced conditions in a forced 
circulation system are more detrimental to satisfactory operation than in 
the system circulated by gravity. The selection of orifices for correcting 
the unbalance must be more accurate. Due to the variations in water 
delivery from pipes, the accuracy of calculations is decreased, so that 
more reliance must be placed on actual test work. This is always costly 
and seldom completely satisfactory. 

A comparison of Fig. 1 and Fig. 2 may suggest that a reversed return 
system requires considerably longer mains than a direct return system. 
This is not always the case, as will be noted from the reversed return 
system of Fig. 3. 

MECHANICAL CIRCULATION AND CIRCULATORS 

The designer of a forced circulation system generally makes use of the 
pumps commercially available. Pumps of this type will have character- 
istics which govern the water velocity selected for the heating system. 
However, available pumps generally have a sufficient range of capacities 

333 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



to promote the selection of an economical velocity. If a system is designed 
to handle a load of 96 Mbh with a 20 F drop allowable in the system, a 
circulating pump will be required, handling about 10 gpm and at a head 
pressure high enough to allow a satisfactory friction drop in the system. 
Frequently water velocities are selected w r hich produce objectionable 
noises in the system. A velocity of over 4 fps is apt to cause noise in the 
smaller pipes and tubes. Velocities higher than this value will cause no 
objectionable trouble in industrial applications. 




HlOMbhH" 



FIG. 3. A FORCED CIRCULATION REVERSED RETURN SYSTEM** 

*Note that the numbers on the radiators indicate thousands of Btu per hour (Mbh) and not square feet. 

Low head centrifugal pumps especially designed for hot water sys- 
tems are used to provide the necessary head pressure for forced circulation 
ind to improve the operation of an improperly designed or installed 
gravity system. These pumps are designated by the nominal pipe size of 
iieir connection, but the selection of the pump should be governed by 
the capacity curves and not by the npminal pipe size. These pumps 
pperate with little noise and low power consumption, both of which are 
Matures of prime importance to the satisfactory operation of a forced 



CHAPTER 17. HOT WATER HEATING SYSTEMS AND PIPING 

circulation system. They are designed for installation directly into the 
heating main and require no other support. The common practice is to 
install them in the return line but where desirable there is no objection to 
their location in the supply line. Gate valves should be installed in either 
side of the pump so that it can be removed without draining a system. 
A by-pass is not necessary as the friction drop through the pump' is not 
sufficient to prevent gravity recirculation if the pump should become 
inoperative. 

Propeller type pumps are also available for hot water service, generally 
being built into a fitting and are made in all of the commercial pipe sizes 
commonly used in heating. They are installed in the same manner as a 
centrifugal pump. 

Forced circulation lends itself to automatic control and the arrangement 
of the circuit depends entirely on the design of the system. The control 
may consist of a thermostat controlling both the automatic firing device 
and the circulator with the same type of limit control, as a safety switch. 
This type of control can be satisfactory, provided the radiation is properly 
selected and accurately located in the building. A circuit using flow 
control valves to regulate the gravity flow of the water when the pump 
is not running allows the temperature to be maintained closer to the 
desired setting. Under these circumstances, the circulator motor is 
controlled by a room thermostat while the automatic firing device is 
controlled by a limit switch with a safety device in 'series. 

For exceptionally large installations, such as central heating plants 
circulating pumps of the centrifugal single stage type having an average 
operating efficiency of 70 per cent against heads up to 125 ft are sometimes 
used. In some cases it is advisable to install pumps in duplicate to provide 
for contingencies and to insure continuous operation. In such cases, 
each pump should be made equal to the maximum capacity required. 

PIPE SIZES 

The pressure heads available in forced circulation systems are much 
greater than those in gravity circulation systems, consequently, higher 
velocities may be used in designing the system, with the result that smaller 
pipes may be selected and the first cost of the installation reduced. As 
the pipes of a heating system are reduced in size, the necessary increase in 
the velocity of the water increases both the cost of operation and the 
initial cost of the circulating equipment. The increased velocity of a 
forced circulation system offers a number of advantages, such as a much 
shorter heating-up period and a more flexible control of hot water circu- 
lation. This improved performance merits the small increase in operating 
cost necessary to mechanically circulate the system. The velocity 
required should be determined by calculation for the particular system 
under consideration. 

Since the velocities in forced circulation systems are higher than those 
in gravity circulation systems, and since the friction heads in a heating 
system vary almost as the squares of the velocities, a given error in the 
calculation or assumption of a velocity is less important in a forced circu- 
lation system than in a gravity circulation system and, consequently, it 

335 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 




50 100 500 1000 

HlTAT CONVEYED PEP HOUP IN 1000 D.T.U. 



5000 10000 



FIG. 4. FRICTION HEADS IN BLACK IRON PIPES FOR A 20 F TEMPERATURE 
DIFFERENCE OF THE WATER IN THE FLOW AND RETURN LINES 



336 



CHAPTER 17. HOT WATER HEATING SYSTEMS AND PIPING 

is easier to design a satisfactory forced circulation system than a satis- 
factory gravity circulation system. 

FORCED CmCULATION 

In designing a forced circulation system, black iron pipe sizes may be 
selected from either Fig. 4 or Table 1, both of which are based on a 20 F 
temperature difference between the flow and return lines. For other 
temperature drops, the pipe capacities may be changed to correspond 
to the desired differentials. Research data are lacking for determining 
the capacities of copper tube sizes. In the absence of complete test data 
at the present time, capacities are given in Table 2 for type L copper tube 
sizes which are based on a recently developed hydraulic formula 1 . The 
friction heads of boiler, radiator valve and tee may be expressed in terms 
of friction head in one elbow according to the values given in Table 3 for 
iron pipe, and Table 4 for copper tubing. 

The following examples will illustrate the procedure to be followed in 
designing forced circulation systems. 

Example 1. From the plan of Fig. 3 note that the longest circuit consists of 151 ft of 
iron pipe; 1 boiler; 1 radiator; 1 radiator valve; 1 stop cock; 10 ells and 3 tees; and the 
shortest circuit consists of 127 ft of pipe; 4 tees; 1 boiler; 1 radiator; 1 radiator valve; 
1 stop cock; and 6 ells. Design the piping for this system. 

Solution. The friction in the various fittings can be expressed in terms of the friction 
in a 90-deg elbow from the values given in Table 3. The longest circuit consists of 151 ft 
of pipe and 44 elbow equivalents. The short circuit consists of 127 ft of pipe and 39 
elbow equivalents. 

The friction head in one elbow is approximately equal to the friction produced by the 
same sized pipe 25 diameters in length. Assume that the average pipe size for this 
system is 1 in. The equivalent length of the longest circuit will be 151 ft plus 100 ft or 
251 ft of pipe. The equivalent length of the short circuit will be 217 ft. 

Having determined the equivalent length of the circuits, the next step is to assume the 
rate at which the water is to be circulated in the system. The water may flow through 
the system so that it will cool any reasonable number of degrees. For the most economi- 
cal average system a 20 F drop seems to be a satisfactory rate. This entails a slower 
water flow from the pumping equipment with a reasonable relationship between pipe 
size and flow. Assume 20 F drop for this system. One gallon of water per minute with a 
density of 7.99 at 215 F will deliver approximately 9600 Btu per hour with a 20 F drop. 
The total radiation load is 98 Mbh, therefore the pump must deliver 10.2 gpm or 4900 
Ib of water per hour. 

Knowing that the rate of flow is 10.2 gpm, the next step is to determine from the 
characteristics of available pumps, which one will produce a satisfactory velocity in the 
system. Assume that 4 pumps are available for this load which will produce 10.2 gpm at 
pressure heads of 2, 5, 10 and 18 ft. At these heads the pumps would produce a velocity 
high enough to make available a friction head per foot of pipe of 96, 240, 480 and 860 
milinches per foot respectively. If 95 milinches per foot were used, the gravity head at 
215 F average temperature in the mains would be 26 per cent of the total head and 
should be considered in sizing the system. At 240 milinches per foot the gravity effect is 
10 per cent and as this is lower than the delivery variation from the pipe used, it can be 
neglected. At 480 and 860 milinches the gravity effect is still a smaller percentage of 
the total, but at these losses in the average system the cost of pumping will more than 
offset the advantage gained in pipe sizes. Therefore, pipe size this system at 240 mil- 
inches per foot which is equivalent to a total loss of 60,000 milinches for the 250 ft 
equivalent length of pipe. 



Hydraulic Service Characteristics of Small Metallic Pipes, by G. M. Fair, M. C. Whipple and C. Y. 
Hsiao (Journal of the Xew England Water Works Association, Vol. XLIV, No. 4, 1930). 

337 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 



TABLE 1. CAPACITIES FOR BLACK IRON PIPE 
A = Carrying capacities inMbh 
B = Velocity in inches per second 



HEAD 
Loss, 
FT 


MlLINCH 


FRICTION Loss 


PER FOOT 


OF PIPE 


720 480 | 360 300 

I 


240 


j 180 

i 


160 | 144 


120 | 

i 


96 


90 ! 80 

l 


70 


60 



EQUIVALENT LENGTH OF PIPE IN FEET (LONGEST CIRCUIT) 



2 33 
2J 42 
3 50 


50 
62 
75 


66 
84 
100 


SO 
100 
120 


100 
125 
150 


133 
167 
200 


150 
188 
225 


167 
208 
250 


200 
250 
300 


250 
312 
375 


270 
333 
400 


300 
375 
450 


340 
428 
510 


400 
500 
600 


3* 

4H 


59 
67 
75 


87 
100 
112 


117 
133 
149 


140 
160 
180 


175 
200 
225 


233 
266 
300 


263 
300 
338 


291 
333 
374 


350 
400 
450 


437 
500 
562 


463 
533 
593 


525 
600 
675 


593 

685 
758 


700 
800 
900 


5 

5* 


83 
02 
100 


125 
137 
150 


167 
183 
200 


200 
220 
240 


250 
275 
300 


333 
366 
400 


375 
413 
450 


416 
457 
500 


500 
550 
600 


625 
687 
750 


666 
713 
800 


750 
825 
900 


860 
923 
1030 


1000 
1100 
1200 




7M 


108 
116 
124 


162 
175 
187 


217 
233 
249 


260 
280 
300 


325 
350 
375 


433 
465 
500 


488 
525 
563 


540 
580 
623 


650 
700 
750 


812 
875 
937 


843 
933 
973 


975 
1050 
1125 


1088 
1200 
1252 


1300 
1400 
1500 


8 
8M 


133 
142 
150 


200 
212 
225 


266 
283 
300 


320 
340 
360 


400 
425 
450 


533 
566 
600 


600 
638 
675 


666 
706 
750 


800 
850 
900 


1000 
1062 
1125 


1070 
1103 
1200 


1200 
1275 
1350 


1370 
1417 
1540 


1600 
1700 
1800 


&* 

10H 


159 
167 
175 


237 
250 
262 


317 
333 
349 


380 
400 
420 


475 
500 
525 


633 
666 
700 


713 
750 

788 


789 
833 
872 


950 
1000 
1050 


1187 
1250 
1312 


1233 
1333 
1363 


1425 
1500 
1575 


1577 
1715 
1737 


1900 
2000 
2100 


11 
11H 

12 


183 
192 
200 


275 
287 
300 


366 
383 
400 


440 
460 
480 


550 
575 
600 


733 
766 
800 


825 
863 
900 


916 
955 
1000 


1100 
1150 
1200 


1375 
1437 
1500 


1466 
1533 
1600 


1650 
1725 
1800 


1885 
1897 
2030 


2200 
2300 
2400 


NOMINAL 
PIPE SIZE, 
IN. 


CAPACITY OF PIPES Mbh WITH A 20 F* DROP 


A 
>* B 


20 

27 


16 

2 


14 
19 


13 

17 


11 
15 


10 
IS 


9 

12 


9 
11 


8 
10 


7 
9 


7 
9 


6 
5 


6 
5 


5 

7 


A 

J* -B 


43 
S3 


35 

So 


30 

23 


27 

21 


24 
18 


21 
16 


19 
15 


18 
14 


17 
IS 


15 
11 


14 
11 


13 

10 


12 
9 


11 
9 


A 
1 B 


85 
39 


70 
32 


60 

27 


54 
25 


48 
22 


41 

19 


39 
18 


36 

17 


33 

15 


30 

IS 


28 
IS 


27 

12 


25 

11 


23 
10 


Itf B 


ISO 
48 


145 
39 


125 
S3 


115 
SO 


98 

27 


85 
S3 


80 
1 


75 

SO 


68 
19 


60 
16 


58 
15 


55 

15 


51 
14 


47 
12 


A 
U* B 


285 

54 


230 
44 


195 
S8 


180 
54 


160 
SO 


135 
86 


125 
4 


120 

23 


110 
SI 


96 

19 


92 
18 


88 
17 


82 
15 


75 
U 


A 
2 B 


540 
64 


435 

52 


370 

45 


340 

40 


300 

36 


255 
SO 


240 

29 


230 

27 


205 

24 


180 

22 


175 

21 


165 
SO 


150 
19 


140 
17 


A 
2^ B 


890 
74 


720 
60 


610 
SO 


550 

46 


480 
41 


420 
35 


390 
33 


370 

31 


330 

25 


300 

54 


280 

*4 


270 

22 


250 

21 


230 
15 


A 
3 B 


1650 
88 


1340 
70 


1130 
60 


1000 
54 


900 
48 


760 
41 


720 

35 


670 

36 


600 
33 


540 

29 


520 
28 


480 
26 


450 
*4 


410 

22 


A 
3H B 


2500 
99 


2000 
78 


1700 

00 


1500 
60 


1350 
a'4 


1150 
40 


1080 

43 


1000 
40 


900 
30 


800 

35 


760 
31 


720 

29 


670 

27 


620 

55 


A 

4 B 


3500 
110 


2800 
87 


2400 
74 


2200 

00 


1900 
J5 


1600 
50 


1520 

47 


1440 

45 


1300 
40 


1150 
35 


1100 
34 


1050 
35 


960 

SO 


880 
57 


A 

5 B 


7000 
132 


5600 
106 


4700 
90 


4300 
80 


3700 
70 


3200 
60 


3000 
56 


2750 
53 


2500 
45 


2200 
42 


2100 

41 


2000 
35 


1800 
35 


1700 
32 


A 
6 B 


12,000 
156 


9200 

i4?4 


7800 
104 


7000 
54 


6200 
55 


5200 
03 


4800 
04 


4600 

01 


4100 
5J 


3600 
45 


3500 
40 


3300 
44 


3000 

41 


2800 

37 


"For other temperature drops the pipe capacities may be changed correspondingly. For example, with 
a. temperature drop of 30 F, the capacities shown in this table are to be multiplied by 1.5. 



338 



CHAPTER 17. 


HOT WATER HEATING SYSTEMS AND PIPING 






TAIILE 


2. CAPACITIES FOR TYPE L COPPER TIDE 
A = Carrying capacity in Mbh 
B Velocity in inches per second 


MILIKCH FRICTION Loss PER FOOT or TUBE 


HEAD 

LOSS 
FT 


7JO 


600 4SO 


360 


300 


240 


ISO 


150 ILU 00 


75 60 


EQUIVALENT LENGTH 


OF TUBE 


IN FEET 


(LONGEST ClKCl'IT 




o 

3'" 


; 33 

i 42 
I 50 


40 50 1 
50 ; 63 i 
60 i 75 i 


67 
83 
100 


80 
100 
120 


100 
, 125 
150 


133 , 
167 , 

200 : 


1*50 , 200 207 
200 250 333 
240 300 i 400 ' 


3^0 , 400 
400 ' 500 
4SO GOO 



33 a 5S 
4 67 
4f2 ( . 75 


70 
SO 
90 


SS ! 117 , 140 175 233 2bO 350 467 560 
100 133 160 ! 200 ' 2C7 320 ; 400 533 040 
113 150 ISO 225 300 ; 3GO 450 , 600 ! 720 


700 
800 
900 


5 
5i a 
6 


83 
92 
100 


100 
110 
120 


125 
138 
150 


167 200 
183 220 
200 240 


250 333 ; 400 500 667 \ 800 1000 
275 . 367 44U I 550 : 733 SSO , 1100 
300 j 400 480 GOO SOO ItfO , 1200 


61-5 

?H 


10S 
117 
125 


130 
140 
150 


163 
175 

188 


217 260 
233 280 
250 300 


325 ! 433 
350 i 467 
375 j 500 


520 r 650 807 
560 700 933 
600 750 ; 1000 


1040 
1120 
1200 


1300 
1400 
1500 


8 

8* 


133 
142 
150 


160 
170 
180 


200 
213 
225 


267 
283 
300 


320 
340 
360 


400 533 
425 i 567 
450 600 


640 
680 
720 


SOO 
850 
900 


1067 
1133 
1200 


1280 
1360 
1440 


1600 
1700 
1800 


18* 

io l A 


159 
167 
175 


190 
200 
210 


238 
250 
263 


317 
333 
350 


380 
400 
420 


475 
500 
525 


633 
667 
700 


760 
800 
840 


950 ; 
1000 
1050 


1267 
1333 
1400 


1520 
1600 
16SO 


1900 
2000 
2100 


11 
n^ 

12 


183 
192 
200 


220 
230 
240 


275 

288 
300 


367 
383 
400 


440 
460 
480 


550 
575 
600 


733 
767 
800 


880 
920 
960 


1100 
1150 
1200 


1467 
1533 
1600 


1760 
1840 j 
1920 


2200 
2300 
2400 


NOMINAL 
TUBE 
SIZE, IN. 


CAPACITY OF TUBES Mbh WITH A 20 F* DROP 


A 
*A B 


10 
7 


9 

24 


8 
21 


6.8 i 6.2 
18 | 16.5 


5.4 
14 


4.6 
13 


4 
11 


3.6 

10 


3 
8.5 


2.8 
8 


2.4 

7 


A 
K B 


20 
53 


18 
SO 


16 
25 


13.5 

21 


8 


10.8 
17 


9 
15 


8 
IS 


7 
12 


6 
10 


5.4 

9 


4.7 


A 
5 A B 


36 
57 


30 

34 


26 
50 


22.1 

24 


20 

21 


17.8 
19 


15 
17 


13.1 
15 


11.8 
13 


9.9 
11 


9 
10 


7.9 

9 


A 
5 


51 
42 


46 
38 


40 
55 


34 

27 


31 

24 


28 

SI 


23.2 

19 


20.5 

17 


1S.1 
14 


15.3 
12 


13.9 
11.5 


12.1 

to 


A 
1 B 


104 
48 


94 
4$ 


82 

89 


70 
34 


63 

50 


56 
25 


47 
22 


42 

19 


37 

17 


32 

14-5 


28 j 25 
13 12 


A 

IK B 


185 
55 


169 
51 


149 
45 


125 
3d 


112 
55 


100 
SO 


84 
5 


75 
S2 


66 
19 


56 
17 


50 
15 


44 
IS 


A 

1H 3 


300 
62 


270 

or 


235 
51 


200 
43 


180 
SO 


160 
5J 


134 
50 


120 
25 


105 

m 


90 
19 


81 71 
17 15 


A 
2 B 


625 
76 


560 
68 


495 
59 


420 375 

51 \ 47 


335 

& 


280 
S6 


250 
S3 


200 

27 


188 

22 


170 
20 


150 
18 


A 
2H B 


1130 
90 


1010 
50 


890 

69 


750 
58 


680 

49 


600 
47 


500 

42 


450 
$7 


395 
55 


335 

26 


305 
23 


270 

21 


A 
3 B 


1840 
98 


1650 
50 


1450 
80 


1210 
66 


1100 
59 


980 
52 


820 

47 


740 

42 


650 
36 


550 
50 


490 

27 


420 

S3 


A 
3H B 


2750 

no 


2480 
100 


2170 
89 


1840 
75 


1650 
66 


1450 
57 


1210 
51 


1100 

43 


980 
40 


820 
So 


740 
30 


650 

26 


A 
4 B 


3900 
120 


3505 
W 


3100 
96 


2600 
83 


2350 
75 


2090 
63 


1760 
55 


15SO 
49 


1390 
44 


1180 
57 


1080 

34 


950 
29 



*For other temperature drops the pipe capacities may be changed correspondingly. For example, with 
i temperature drop of 30 F, the capacities shown in this table are to be multiplied by 1.5. 



339 



HEATING VENTILATING AIR CONDITIONING GUIDE 1938 

TABLE 3. IRON ELBOW EQUIVALENTS 5 * 

1 90-deg elbow 1 Q 

1 45-deg elbow ~~. Q? 

1 90-deg long turn elbow._ 9*5 

1 open return bend._ " J|